# A. Nikolaev - A2 Collaboration at MAMI

## Contact Details

NameA. Nikolaev |
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AffiliationA2 Collaboration at MAMI |
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Location |
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## Pubs By Year |
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## External Links |
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## Pub CategoriesNuclear Experiment (21) High Energy Physics - Lattice (11) High Energy Physics - Experiment (9) Nuclear Theory (6) Computer Science - Computational Complexity (5) Mathematics - Group Theory (5) Physics - Strongly Correlated Electrons (5) High Energy Physics - Phenomenology (4) Mathematics - Combinatorics (4) General Relativity and Quantum Cosmology (3) Mathematics - Mathematical Physics (3) Mathematical Physics (3) Nonlinear Sciences - Chaotic Dynamics (2) Physics - Mesoscopic Systems and Quantum Hall Effect (2) Mathematics - Dynamical Systems (2) Physics - Materials Science (2) Nonlinear Sciences - Exactly Solvable and Integrable Systems (1) High Energy Physics - Theory (1) Cosmology and Nongalactic Astrophysics (1) Mathematics - Analysis of PDEs (1) Quantum Physics (1) Physics - Chemical Physics (1) |

## Publications Authored By A. Nikolaev

We investigate the potential for using the canonical ensemble approach to determine the QCD phase diagram in the temperature - density plane. This approach allows us to study the finite baryon density regions where the well-known sign problem obstructs the standard lattice QCD numerical study. Using the canonical ensemble approach, we perform lattice QCD simulations at the pure imaginary quark chemical potential. Read More

We consider a group-theoretic analogue of the classic subset sum problem. It is known that every virtually nilpotent group has polynomial time decidable subset sum problem. In this paper we use subgroup distortion to show that every polycyclic non-virtually-nilpotent group has NP-complete subset sum problem. Read More

This work explores a structure of the Deprit perturbation series and its connection to a Kato resolvent expansion. It extends the formalism previously developed for the Hamiltonians linearly dependent on perturbation parameter to a nonlinear case. We construct a canonical intertwining of perturbed and unperturbed averaging operators. Read More

New approach to computation of canonical partition functions in $N_f=2$ lattice QCD is presented. We compare results obtained by new method with results obtained by known method of hopping parameter expansion. We observe agreement between two methods indicating validity of the new method. Read More

The canonical approach, which was developed for solving the sign problem, may suffer from a new type of sign problem. In the canonical approach, the grand partition function is written as a fugacity expansion: $Z_G(\mu,T) = \sum_n Z_C(n,T) \xi^n$, where $\xi=\exp(\mu/T)$ is the fugacity, and $Z_C(n,T)$ are given as averages over a Monte Carlo update, $\langle z_n\rangle$. We show that the complex phase of $z_n$ is proportional to $n$ at each Monte Carlo step. Read More

At finite baryon density lattice QCD first-principle calculations can not be performed due to the sign problem. In order to circumvent this problem, we use the canonical approach, which provides reliable analytical continuation from the imaginary chemical potential region to the real chemical potential region. We briefly present the canonical partition function method, describe our formulation, and show the results, obtained for two temperatures: $T/T_c = 0. Read More

We study lattice QCD with $N_f=2$ Wilson fermions at nonzero imaginary chemical potential and nonzero temperature. We relate the Roberge - Weiss phase transition to the properties of dyons which are constituents of the KvBLL calorons. We present numerical evidence that the characteristic features of the spectral gap of the overlap Dirac operator as function of an angle modifying the boundary condition are determined by the $Z_3$ sector of the respective imaginary chemical potential. Read More

**Authors:**P. Adlarson, F. Afzal, P. Aguar-BartolomÃ©, Z. Ahmed, C. S. Akondi, J. R. M. Annand, H. J. Arends, K. Bantawa, R. Beck, H. BerghÃ¤user, M. Biroth, N. S. Borisov, A. Braghieri, W. J. Briscoe, S. Cherepnya, F. Cividini, C. Collicott, S. Costanza, A. Denig, M. Dieterle, E. J. Downie, P. Drexler, M. I. Ferretti Bondy, L. V. Fil'kov, S. Gardner, S. Garni, D. I. Glazier, D. Glowa, W. Gradl, G. M. Gurevich, D. J. Hamilton, D. Hornidge, G. M. Huber, T. C. Jude, A. KÃ¤ser, V. L. Kashevarov, S. Kay, I. Keshelashvili, R. Kondratiev, M. Korolija, B. Krusche, V. V. Kulikov, A. Lazarev, J. Linturi, V. Lisin, K. Livingston, I. J. D. MacGregor, R. Macrae, D. M. Manley, P. P. Martel, M. Martemianov, J. C. McGeorge, E. F. McNicoll, V. Metag, D. G. Middleton, R. Miskimen, E. Mornacchi, C. Mullen, A. Mushkarenkov, A. Neganov, A. Neiser, A. Nikolaev, M. Oberle, M. Ostrick, P. Ott, P. B. Otte, D. Paudyal, P. Pedroni, A. Polonski, S. Prakhov, A. Rajabi, J. Robinson, G. Ron, G. Rosner, T. Rostomyan, C. Sfienti, M. H. Sikora, V. Sokhoyan, K. Spieker, O. Steffen, I. I. Strakovsky, B. Strandberg, Th. Strub, I. Supek, A. Thiel, M. Thiel, A. Thomas, M. Unverzagt, Yu. A. Usov, S. Wagner, N. Walford, D. P. Watts, D. WerthmÃ¼ller, J. Wettig, L. Witthauer, M. Wolfes, L. A. Zana

The Dalitz decay pi^0 -> e^+e^-gamma has been measured in the gamma p -> pi^0 p reaction with the A2 tagged-photon facility at the Mainz Microtron, MAMI. The value obtained for the slope parameter of the pi^0 electromagnetic transition form factor, a_pi = 0.030+/-0. Read More

We propose and test a new approach to computation of canonical partition functions in lattice QCD at finite density. We suggest a few steps procedure. We first compute numerically the quark number density for imaginary chemical potential $i\mu_{qI}$. Read More

Following the seminal work of Padberg on the Boolean quadric polytope $BQP$ and its LP relaxation $BQP_{LP}$, we consider a natural extension: $SATP$ and $SATP_{LP}$ polytopes, with $BQP_{LP}$ being projection of the $SATP_{LP}$ face (and $BQP$ -- projection of the $SATP$ face). We consider a problem of integer recognition: determine whether a maximum of a linear objective function is achieved at an integral vertex of a polytope. Various special instances of 3-SAT problem like NAE-3-SAT, 1-in-3-SAT, weighted MAX-3-SAT, and others can be solved by integer recognition over $SATP_{LP}$. Read More

We look for exact solutions in scalar field cosmology. To achieve this we use $f(R)$ modified gravity with a scalar field and do not specify the the form of the $f(R)$ function. In particular, we study Friedmann universe assuming that acceleration of the scalar curvature is negligible. Read More

We observe a series of sharp resonant features in the tunnelling differential conductance of InAs quantum dots. We found that dissipative quantum tunnelling has a strong influence on the operation of nano-devices. Because of such tunnelling the current-voltage characteristics of tunnel contact created between atomic force microscope tip and a surface of InAs/GaAs quantum dots display many interesting peaks. Read More

**Authors:**P. Adlarson, F. Afzal, P. Aguar-BartolomÃ©, Z. Ahmed, J. R. M. Annand, H. J. Arends, K. Bantawa, R. Beck, H. BerghÃ¤user, M. Biroth, N. S. Borisov, A. Braghieri, W. J. Briscoe, S. Cherepnya, F. Cividini, C. Collicott, S. Costanza, I. V. Danilkin, A. Denig, M. Dieterle, E. J. Downie, P. Drexler, M. I. Ferretti Bondy, L. V. Fil'kov, S. Gardner, S. Garni, D. I. Glazier, D. Glowa, W. Gradl, G. M. Gurevich, D. J. Hamilton, D. Hornidge, G. M. Huber, T. C. Jude, A. KÃ¤ser, V. L. Kashevarov, S. Kay, I. Keshelashvili, R. Kondratiev, M. Korolija, B. Krusche, A. Lazarev, J. Linturi, V. Lisin, K. Livingston, I. J. D. MacGregor, R. Macrae, D. M. Manley, P. P. Martel, J. C. McGeorge, E. F. McNicoll, V. Metag, D. G. Middleton, R. Miskimen, E. Mornacchi, C. Mullen, A. Mushkarenkov, A. Neganov, A. Neiser, A. Nikolaev, M. Oberle, M. Ostrick, P. Ott, P. B. Otte, D. Paudyal, P. Pedroni, A. Polonski, S. Prakhov, A. Rajabi, J. Robinson, G. Ron, G. Rosner, T. Rostomyan, C. Sfienti, M. H. Sikora, V. Sokhoyan, K. Spieker, O. Steffen, I. I. Strakovsky, B. Strandberg, Th. Strub, I. Supek, A. Thiel, M. Thiel, A. Thomas, M. Unverzagt, Yu. A. Usov, S. Wagner, N. Walford, D. P. Watts, D. WerthmÃ¼ller, J. Wettig, L. Witthauer, M. Wolfes, L. A. Zana

The Dalitz decays eta -> e^+e^-g and omega -> pi^0 e^+e^- have been measured in the g p -> eta p and g p -> omega p reactions, respectively, with the A2 tagged-photon facility at the Mainz Microtron, MAMI. The value obtained for the slope parameter of the electromagnetic transition form factor of eta, Lambda^{-2}_eta=(1.97+/-0. Read More

**Authors:**A. Kaeser, F. Mueller, J. Ahrens, J. R. M. Annand, H. J. Arends, K. Bantawa, P. A. Bartolome, R. Beck, A. Braghieri, W. J. Briscoe, S. Cherepnya, S. Costanza, M. Dieterle, E. J. Downie, P. Drexler, L. V. Fil'kov, A. Fix, S. Garni, D. I. Glazier, D. Hamilton, D. Hornidge, D. Howdle, G. M. Huber, I. Jaegle, T. C. Jude, V. L. Kashevarov, I. Keshelashvili, R. Kondratiev, M. Korolija, B. Krusche, V. Lisin, K. Livingston, I. J. D. MacGregor, Y. Maghrbi, J. Mancell, D. M. Manley, Z. Marinides, J. C. McGeorge, E. McNicoll, D. Mekterovic, V. Metag, S. Micanovic, D. G. Middleton, A. Mushkarenkov, A. Nikolaev, R. Novotny, M. Oberle, M. Ostrick, P. Otte, B. Oussena, P. Pedroni, F. Pheron, A. Polonski, S. Prakhov, J. Robinson, T. Rostomyan, S. Schumann, M. H. Sikora, D. Sober, A. Starostin, Th. Strub, I. Supek, M. Thiel, A. Thomas, M. Unverzagt, N. K. Walford, D. P. Watts, D. Werthmueller, L. Witthauer

**Category:**Nuclear Experiment

Quasi-free photoproduction of $\pi\eta$-pairs has been investigated from threshold up to incident photon energies of 1.4 GeV, respectively up to photon-nucleon invariant masses up to 1.9 GeV. Read More

In this paper the phase diagram of Dirac semimetals is studied within lattice Monte-Carlo simulation. In particular, we concentrate on the dynamical chiral symmetry breaking which results in semimetal/insulator transition. Using numerical simulation we determined the values of the critical coupling constant of the semimetal/insulator transition for different values of the anisotropy of the Fermi velocity. Read More

The problem of bubble domain generation is revisited from a new perspective that was opened by recent findings in the field of physics of magnetic skyrmions. The single bubble domain can be generated under the tip electrode touching the surface of dielectric iron garnet film by positive step-like voltage pulse and its equilibrium size can be increased with further rising of electric potential. The theoretical analysis shows that the same mechanism can be used to stabilize the submicron bubbles topologically equivalent to the skyrmion. Read More

**Authors:**S. Gardner, D. Howdle, M. H. Sikora, Y. Wunderlich, S. Abt, P. Achenbach, F. Afzal, P. Aguar-Bartolome, Z. Ahmed, J. R. M. Annand, H. J. Arends, K. Bantawa, M. Bashkanov, R. Beck, M. Biroth, N. S. Borisov, A. Braghieri, W. J. Briscoe, S. Cherepnya, F. Cividini, S. Costanza, C. Collicott, B. T. Demissie, A. Denig, M. Dieterle, E. J. Downie, P. Drexler, M. I. Ferretti-Bondy, L. V. Filkov, D. I. Glazier, S. Garni, W. Gradl, M. GÃ¼nther, G. M. Gurevich, D. Hamilton, E. Heid, D. Hornidge, G. M. Huber, O. Jahn, T. C. Jude, A. KÃ¤ser, S. Kay, V. L. Kashevarov, I. Keshelashvili, R. Kondratiev, M. Korolija, B. Krusche, J. M. Linturi, V. Lisin, K. Livingston, S. Lutterer, I. J. D. MacGregor, R. Macrae, J. Mancell, D. M. Manley, P. P. Martel, J. C. McGeorge, E. F. McNicoll, D. G. Middleton, R. Miskimen, C. Mullen, A. Mushkarenkov, A. B. Neganov, A. Neiser, A. Nikolaev, M. Oberle, M. Ostrick, R. O. Owens, P. B. Otte, B. Oussena, D. Paudyal, P. Pedroni, A. Polonski, S. Prakhov, A. Rajabi, J. Robinson, G. Rosner, T. Rostomyan, A. Sarty, S. Schumann, V. Sokhoyan, K. Spieker, O. Steffen, C. Sfienti, I. I. Strakovsky, B. Strandberg, Th. Strub, I. Supek, C. M. Tarbert, A. Thiel, M. Thiel, A. Thomas, M. Unverzagt, Yu. A. Usov, D. P. Watts, D. WerthmÃ¼ller, J. Wettig, M. Wolfes, L. Witthauer, L. Zana

**Category:**Nuclear Experiment

High statistics measurements of the photon asymmetry $\mathrm{\Sigma}$ for the $\overrightarrow{\gamma}$p$\rightarrow\pi^{0}$p reaction have been made in the center of mass energy range W=1214-1450 MeV. The data were measured with the MAMI A2 real photon beam and Crystal Ball/TAPS detector systems in Mainz, Germany. The results significantly improve the existing world data and are shown to be in good agreement with previous measurements, and with the MAID, SAID, and Bonn-Gatchina predictions. Read More

The magnetic hyperfine (MHF) structure of the $5/2^+$(0.0 eV) ground state and the low-lying $3/2^+$(7.8 eV) isomeric state of the $^{229}$Th nucleus in highly charged ions Th$^{89+}$ and Th$^{87+}$ is calculated. Read More

In this paper we carry out a low-temperature scan of the phase diagram of dense two-color QCD with $N_f=2$ quarks. The study is conducted using lattice simulation with rooted staggered quarks. At small chemical potential we observe the hadronic phase, where the theory is in a confining state, chiral symmetry is broken, the baryon density is zero and there is no diquark condensate. Read More

Using the focusing equation, the equation for the cosmological angular diameter distance is derived, based on the ideas of Academician Ya.B. Zel'dovich, namely, that the distribution of matter at small angles is not homogeneous, and the light cone is close to being empty. Read More

The lattice simulations of $QC_2D$ with two flavors of staggered fermions and non-zero quark chemical potential $\mu_q$ have been performed. Dependencies of the Polyakov loop, chiral condensate and baryon number density on $\mu_q$ were studied. We found that an increase of the baryon chemical potential leads to chiral symmetry restoration. Read More

**Authors:**M. Dieterle, M. Oberle, J. Ahrens, J. R. M. Annand, H. J. Arends, K. Bantawa, P. A. Bartolome, R. Beck, V. Bekrenev, H. BerghÃ¤user, A. Braghieri, D. Branford, W. J. Briscoe, J. Brudvik, S. Cherepnya, S. Costanza, B. Demissie, E. J. Downie, P. Drexler, L. V. Fil'kov, A. Fix, S. Garni, D. I. Glazier, D. Hamilton, E. Heid, D. Hornidge, D. Howdle, G. M. Huber, O. Jahn, T. C. Jude, A. KÃ¤ser, V. L. Kashevarov, I. Keshelashvili, R. Kondratiev, M. Korolija, B. Krusche, V. Lisin, K. Livingston, I. J. D. MacGregor, Y. Maghrbi, J. Mancell, D. M. Manley, Z. Marinides, J. C. McGeorge, E. McNicoll, D. Mekterovic, V. Metag, S. Micanovic, D. G. Middleton, A. Mushkarenkov, A. Nikolaev, R. Novotny, M. Ostrick, P. Otte, B. Oussena, P. Pedroni, F. Pheron, A. Polonski, S. Prakhov, J. Robinson, T. Rostomyan, S. Schumann, M. H. Sikora, D. I. Sober, A. Starostin, Th. Strub, I. Supek, M. Thiel, A. Thomas, M. Unverzagt, N. K. Walford, D. P. Watts, D. WerthmÃ¼ller, L. Witthauer

**Category:**Nuclear Experiment

Total cross sections, angular distributions, and invariant-mass distributions have been measured for the photoproduction of $\pi^0\pi^0$ pairs off free protons and off nucleons bound in the deuteron. The experiments were performed at the MAMI accelerator facility in Mainz using the Glasgow photon tagging spectrometer and the Crystal Ball/TAPS detector. The accelerator delivered electron beams of 1508 and 1557~MeV, which produced bremsstrahlung in thin radiator foils. Read More

Stationary solutions on a bounded interval for an initial-boundary value problem to Korteweg--de~Vries and modified Korteweg--de~Vries equation (for the last one both in focusing and defocusing cases) are constructed. The method of the study is based on the theory of conservative systems with one degree of freedom. The obtained solutions turn out to be periodic. Read More

We consider several subgroup-related algorithmic questions in groups, modeled after the classic computational lattice problems, and study their computational complexity. We find polynomial time solutions to problems like finding a subgroup element closest to a given group element, or finding a shortest non-trivial element of a subgroup in the case of nilpotent groups, and a large class of surface groups and Coxeter groups. We also provide polynomial time algorithm to compute geodesics in given generators of a subgroup of a free group. Read More

**Authors:**A. KÃ¤ser, J. Ahrens, J. R. M. Annand, H. J. Arends, K. Bantawa, P. A. Bartolome, R. Beck, V. Bekrenev, H. BerghÃ¤user, A. Braghieri, D. Branford, W. J. Briscoe, J. Brudvik, S. Cherepnya, S. Costanza, B. Demissie, M. Dieterle, E. J. Downie, P. Drexler, L. V. Fil'kov, A. Fix, D. I. Glazier, D. Hamilton, E. Heid, D. Hornidge, D. Howdle, G. M. Huber, O. Jahn, I. Jaegle, T. C. Jude, V. L. Kashevarov, I. Keshelashvili, R. Kondratiev, M. Korolija, S. P. Kruglov, B. Krusche, V. Lisin, K. Livingston, I. J. D. MacGregor, Y. Maghrbi, J. Mancell, D. M. Manley, Z. Marinides, J. C. McGeorge, E. McNicoll, D. Mekterovic, V. Metag, S. Micanovic, D. G. Middleton, A. Mushkarenkov, A. Nikolaev, R. Novotny, M. Oberle, M. Ostrick, P. Otte, B. Oussena, P. Pedroni, F. Pheron, A. Polonski, S. N. Prakhov, J. Robinson, G. Rosner, T. Rostomyan, S. Schumann, M. H. Sikora, D. I. Sober, A. Starostin, I. Supek, M. Thiel, A. Thomas, M. Unverzagt, D. P. Watts, D. WerthmÃ¼ller, L. Witthauer

**Category:**Nuclear Experiment

Photoproduction of $\pi\eta$-pairs from nucleons has been investigated from threshold up to incident photon energies of $\approx$~1.4~GeV. The quasi-free reactions $\gamma p\rightarrow p\pi^0\eta$, $\gamma n\rightarrow n\pi^0\eta$, $\gamma p\rightarrow n\pi^+\eta$, and $\gamma n\rightarrow p\pi^-\eta$ were for the first time measured from nucleons bound in the deuteron. Read More

**Authors:**J. R. M. Annand, H. J. Arends, R. Beck, N. Borisov, A. Braghieri, W. J. Briscoe, S. Cherepnya, C. Collicott, S. Costanza, E. J. Downie, M. Dieterle, A. Fix, L. V. Fil'kov, S. Garni, D. I. Glazier, W. Gradl, G. Gurevich, P. H. Barrientos, D. Hamilton, D. Hornidge, D. Howdle, G. M. Huber, V. L. Kashevarov, I. Keshelashvili, R. Kondratiev, M. Korolija, B. Krusche, A. Lazarev, V. Lisin, K. Livingston, I. J. D. MacGregor, J. Mancel, D. M. Manley, P. Martel, E. F. McNicoll, W. Meyer, D. Middleton, R. Miskimen, A. Mushkarenkov, A. Neganov, A. Nikolaev, M. Oberle, H. Ortega, M. Ostrick, P. Ott, P. B. Otte, B. Oussena, P. Pedroni, A. Polonski, V. V. Polyanski, S. Prakhov, G. Reicherz, T. Rostomyan, A. Sarty, S. Schumann, O. Steffen, I. I. Strakovsky, T. Strub, I. Supek, L. Tiator, A. Thomas, M. Unverzagt, Y. A. Usov, D. P. Watts, D. WerthmÃ¼ller, L. Witthauer, M. Wolfes

The first data on target and beam-target asymmetries for the $\gamma p\to\pi^0\eta p$ reaction at photon energies from 1050 up to 1450 MeV are presented. The measurements were performed using the Crystal Ball and TAPS detector setup at the Glasgow tagged photon facility of the Mainz Microtron MAMI. The general assumption that the reaction is dominated by the $\Delta 3/2^-$ amplitude is confirmed. Read More

We present our development of Zeldovich's ideas for the measurement of the cosmological angular diameter distance (ADD) in the Friedmann Universe. We derive the general differential equation for the ADD measurement which is valid for an open, spatially-flat and closed universe, and for any stress energy tensor. We solve the mentioned equations in terms of quadratures in a form suitable for further numerical investigations for the present universe filled by radiation, (baryonic and dark) matter and dark energy. Read More

This work establishes a connection between canonical perturbation series in quantum mechanics and a Kato expansion for the resolvent of the Liouville superoperator. Our approach leads to an explicit expression for a generator of a block-diagonalizing Dyson's ordered exponential in arbitrary perturbation order. Unitary intertwining of perturbed and unperturbed averaging superprojectors allows for a description of ambiguities in the generator and block-diagonalized Hamiltonian. Read More

In order to increase the accuracy of the linearized augmented plane wave method (LAPW) we present a new approach where the plane wave basis function is augmented by two different atomic radial components constructed at two different linearization energies corresponding to two different electron bands (or energy windows). We demonstrate that this case can be reduced to the standard treatment within the LAPW paradigm where the usual basis set is enriched by the basis functions of the tight binding type, which go to zero with zero derivative at the sphere boundary. We show that the task is closely related with the problem of extended core states which is currently solved by applying the LAPW method with local orbitals (LAPW+LO). Read More

For finitely generated nilpotent groups, we employ Mal'cev coordinates to solve several classical algorithmic problems efficiently. Computation of normal forms, the membership problem, the conjugacy problem, and computation of presentations for subgroups are solved using only logarithmic space and quasilinear time. Logarithmic space presentation-uniform versions of these algorithms are provided. Read More

Tight-binding model of the AA-stacked bilayer graphene with screened electron-electron interactions has been studied using the Hybrid Monte Carlo simulations on the original double-layer hexagonal lattice. Instantaneous screened Coulomb potential is taken into account using Hubbard-Stratonovich transformation. G-type antiferromagnetic ordering has been studied and the phase transition with spontaneous generation of the mass gap has been observed. Read More

The classic knapsack and related problems have natural generalizations to arbitrary (non-commutative) groups, collectively called knapsack-type problems in groups. We study the effect of free and direct products on their time complexity. We show that free products in certain sense preserve time complexity of knapsack-type problems, while direct products may amplify it. Read More

**Authors:**C. S. Akondi, J. R. M. Annand, H. J. Arends, R. Beck, A. Bernstein, N. Borisov, A. Braghieri, W. J. Briscoe, S. Cherepnya, C. Collicott, S. Costanza, E. J. Downie, M. Dieterle, A. Fix, L. V. Fil'kov, S. Garni, D. I. Glazier, W. Gradl, G. Gurevich, P. Hall Barrientos, D. Hamilton, D. Hornidge, D. Howdle, G. M. Huber, V. L. Kashevarov, I. Keshelashvili, R. Kondratiev, M. Korolija, B. Krusche, A. Lazarev, V. Lisin, K. Livingston, I. J. D. MacGregor, J. Mancel, D. M. Manley, P. Martel, E. F. McNicoll, W. Meyer, D. Middleton, R. Miskimen, A. Mushkarenkov, B. M. K. Nefkens, A. Neganov, A. Nikolaev, M. Oberle, M. Ostrick, H. Ortega, P. Ott, P. B. Otte, B. Oussena, P. Pedroni, A. Polonski, V. V. Polyanski, S. Prakhov, G. Reicherz, T. Rostomyan, A. Sarty, S. Schumann, O. Steffen, I. I. Strakovsky, Th. Strub, I. Supek, L. Tiator, A. Thomas, M. Unverzagt, Yu. A. Usov, D. P. Watts, D. WerthmÃ¼ller, L. Witthauer, M. Wolfes

We present new data for the transverse target asymmetry T and the very first data for the beam-target asymmetry F in the $\vec \gamma \vec p\to\eta p$ reaction up to a center-of-mass energy of W=1.9 GeV. The data were obtained with the Crystal-Ball/TAPS detector setup at the Glasgow tagged photon facility of the Mainz Microtron MAMI. Read More

**Authors:**P. P. Martel, R. Miskimen, P. Aguar-Bartolome, J. Ahrens, C. S. Akondi, J. R. M. Annand, H. J. Arends, W. Barnes, R. Beck, A. Bernstein, N. Borisov, A. Braghieri, W. J. Briscoe, S. Cherepnya, C. Collicott, S. Costanza, A. Denig, M. Dieterle, E. J. Downie, L. V. Fil'kov, S. Garni, D. I. Glazier, W. Gradl, G. Gurevich, P. Hall Barrientos, D. Hamilton, D. Hornidge, D. Howdle, G. M. Huber, T. C. Jude, A. Kaeser, V. L. Kashevarov, I. Keshelashvili, R. Kondratiev, M. Korolija, B. Krusche, A. Lazarev, V. Lisin, K. Livingston, I. J. D. MacGregor, J. Mancell, D. M. Manley, W. Meyer, D. G. Middleton, A. Mushkarenkov, B. M. K. Nefkens, A. Neganov, A. Nikolaev, M. Oberle, H. Ortega Spina, M. Ostrick, P. Ott, P. B. Otte, B. Oussena, P. Pedroni, A. Polonski, V. Polyansky, S. Prakhov, A. Rajabi, G. Reicherz, T. Rostomyan, A. Sarty, S. Schrauf, S. Schumann, M. H. Sikora, A. Starostin, O. Steffen, I. I. Strakovsky, T. Strub, I. Supek, M. Thiel, L. Tiator, A. Thomas, M. Unverzagt, Y. Usov, D. P. Watts, L. Witthauer, D. WerthmÃ¼ller, M. Wolfes

**Category:**Nuclear Experiment

The spin polarizabilities of the nucleon describe how the spin of the nucleon responds to an incident polarized photon. The most model-independent way to measure the nucleon spin polarizabilities is through polarized Compton scattering. Double-polarized Compton scattering asymmetries on the proton were measured in the $\Delta(1232)$ region using circularly polarized incident photons and a transversely polarized proton target at the Mainz Microtron. Read More

**Authors:**A2 Collaboration, D. WerthmÃ¼ller, L. Witthauer, I. Keshelashvili, P. Aguar-BartolomÃ©, J. Ahrens, J. R. M. Annand, H. J. Arends, K. Bantawa, R. Beck, V. Bekrenev, A. Braghieri, D. Branford, W. J. Briscoe, J. Brudvik, S. Cherepnya, S. Costanza, B. Demissie, M. Dieterle, E. J. Downie, P. Drexler, L. V. Fil'kov, A. Fix, D. I. Glazier, D. Hamilton, E. Heid, D. Hornidge, D. Howdle, G. M. Huber, I. Jaegle, O. Jahn, T. C. Jude, A. KÃ¤ser, V. L. Kashevarov, R. Kondratiev, M. Korolija, S. P. Kruglov, B. Krusche, A. Kulbardis, V. Lisin, K. Livingston, I. J. D. MacGregor, Y. Maghrbi, J. Mancell, D. M. Manley, Z. Marinides, M. Martinez, J. C. McGeorge, E. F. McNicoll, V. Metag, D. G. Middleton, A. Mushkarenkov, B. M. K. Nefkens, A. Nikolaev, R. Novotny, M. Oberle, M. Ostrick, P. B. Otte, B. Oussena, P. Pedroni, F. Pheron, A. Polonski, S. N. Prakhov, J. Robinson, G. Rosner, T. Rostomyan, S. Schumann, M. H. Sikora, D. Sober, A. Starostin, I. Supek, M. Thiel, A. Thomas, M. Unverzagt, D. P. Watts

Differential and total cross sections for the quasifree reactions $\gamma p\rightarrow\eta p$ and $\gamma n\rightarrow\eta n$ have been determined at the MAMI-C electron accelerator using a liquid deuterium target. Photons were produced via bremsstrahlung from the 1.5 GeV incident electron beam and energy-tagged with the Glasgow photon tagger. Read More

**Authors:**I. I. Strakovsky, S. Prakhov, Y. I. Azimov, P. Aguar-Bartolome, J. R. M. Annand, H. J. Arends, K. Bantawa, R. Beck, V. Bekrenev, H. Berghaeuser, A. Braghieri, W. J. Briscoe, J. Brudvik, S. Cherepnya, R. F. B. Codling, C. Collicott, S. Costanza, B. T. Demissie, E. J. Downie, P. Drexler, L. V. Fil'kov, D. I. Glazier, R. Gregor, D. J. Hamilton, E. Heid, D. Hornidge, I. Jaegle, O. Jahn, T. C. Jude, V. L. Kashevarov, I. Keshelashvili, R. Kondratiev, M. Korolija, M. Kotulla, A. Koulbardis, S. Kruglov, B. Krusche, V. Lisin, K. Livingston, I. J. D. MacGregor, Y. Maghrbi, D. M. Manley, Z. Marinides, J. C. McGeorge, E. F. McNicoll, D. Mekterovic, V. Metag, D. G. Middleton, A. Mushkarenkov, B. M. K. Nefkens, A. Nikolaev, R. Novotny, H. Ortega, M. Ostrick, P. B. Otte, B. Oussena, P. Pedroni, F. Pheron, A. Polonski, J. Robinson, G. Rosner, T. Rostomyan, S. Schumann, M. H. Sikora, A. Starostin, I. Supek, M. F. Taragin, C. M. Tarbert, M. Thiel, A. Thomas, M. Unverzagt, D. P. Watts, D. Werthmueller, F. Zehr

An experimental study of $\omega$ photoproduction on the proton was conducted by using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. The $\gamma p\to\omega p$ differential cross sections are measured from threshold to the incident-photon energy $E_\gamma=1.40$ GeV ($W=1. Read More

Time differential perturbed angular gamma-gamma-correlation (TDPAC) method on 111Cd nuclei probes inserted in ZrZn1.9 is used to measure the magnetic hyperfine fields (MHF) at Zr and Zn sites and the electric field gradient (EFG) Vzz at Zn sites as a function of temperature at various pressures and as a function of pressure at the temperature 4 K. Our data indicate that the local magnetic moment of Zr in the magnetically ordered state is substantially larger than its value obtained from the macroscopic measurements and that there is also an induced magnetic moment at the Zn site. Read More

**Authors:**B. M. K. Nefkens

^{1}, S. Prakhov

^{2}, P. Aguar-BartolomÃ©

^{3}, J. R. M. Annand

^{4}, H. J. Arends

^{5}, K. Bantawa

^{6}, R. Beck

^{7}, V. Bekrenev

^{8}, H. BerghÃ¤user

^{9}, A. Braghieri

^{10}, W. J. Briscoe

^{11}, J. Brudvik

^{12}, S. Cherepnya

^{13}, R. F. B. Codling

^{14}, C. Collicott

^{15}, S. Costanza

^{16}, I. V. Danilkin

^{17}, A. Denig

^{18}, B. Demissie

^{19}, M. Dieterle

^{20}, E. J. Downie

^{21}, P. Drexler

^{22}, L. V. Fil'kov

^{23}, A. Fix

^{24}, S. Garni

^{25}, D. I. Glazier

^{26}, R. Gregor

^{27}, D. Hamilton

^{28}, E. Heid

^{29}, D. Hornidge

^{30}, D. Howdle

^{31}, O. Jahn

^{32}, T. C. Jude

^{33}, V. L. Kashevarov

^{34}, A. KÃ¤ser

^{35}, I. Keshelashvili

^{36}, R. Kondratiev

^{37}, M. Korolija

^{38}, M. Kotulla

^{39}, A. Koulbardis

^{40}, S. Kruglov

^{41}, B. Krusche

^{42}, V. Lisin

^{43}, K. Livingston

^{44}, I. J. D. MacGregor

^{45}, Y. Maghrbi

^{46}, J. Mancel

^{47}, D. M. Manley

^{48}, E. F. McNicoll

^{49}, D. Mekterovic

^{50}, V. Metag

^{51}, A. Mushkarenkov

^{52}, A. Nikolaev

^{53}, R. Novotny

^{54}, M. Oberle

^{55}, H. Ortega

^{56}, M. Ostrick

^{57}, P. Ott

^{58}, P. B. Otte

^{59}, B. Oussena

^{60}, P. Pedroni

^{61}, A. Polonski

^{62}, J. Robinson

^{63}, G. Rosner

^{64}, T. Rostomyan

^{65}, S. Schumann

^{66}, M. H. Sikora

^{67}, A. Starostin

^{68}, I. I. Strakovsky

^{69}, T. Strub

^{70}, I. M. Suarez

^{71}, I. Supek

^{72}, C. M. Tarbert

^{73}, M. Thiel

^{74}, A. Thomas

^{75}, M. Unverzagt

^{76}, D. P. Watts

^{77}, D. WerthmÃ¼ller

^{78}, L. Witthauer.

^{79}

**Affiliations:**

^{1}A2 Collaboration at MAMI,

^{2}A2 Collaboration at MAMI,

^{3}A2 Collaboration at MAMI,

^{4}A2 Collaboration at MAMI,

^{5}A2 Collaboration at MAMI,

^{6}A2 Collaboration at MAMI,

^{7}A2 Collaboration at MAMI,

^{8}A2 Collaboration at MAMI,

^{9}A2 Collaboration at MAMI,

^{10}A2 Collaboration at MAMI,

^{11}A2 Collaboration at MAMI,

^{12}A2 Collaboration at MAMI,

^{13}A2 Collaboration at MAMI,

^{14}A2 Collaboration at MAMI,

^{15}A2 Collaboration at MAMI,

^{16}A2 Collaboration at MAMI,

^{17}A2 Collaboration at MAMI,

^{18}A2 Collaboration at MAMI,

^{19}A2 Collaboration at MAMI,

^{20}A2 Collaboration at MAMI,

^{21}A2 Collaboration at MAMI,

^{22}A2 Collaboration at MAMI,

^{23}A2 Collaboration at MAMI,

^{24}A2 Collaboration at MAMI,

^{25}A2 Collaboration at MAMI,

^{26}A2 Collaboration at MAMI,

^{27}A2 Collaboration at MAMI,

^{28}A2 Collaboration at MAMI,

^{29}A2 Collaboration at MAMI,

^{30}A2 Collaboration at MAMI,

^{31}A2 Collaboration at MAMI,

^{32}A2 Collaboration at MAMI,

^{33}A2 Collaboration at MAMI,

^{34}A2 Collaboration at MAMI,

^{35}A2 Collaboration at MAMI,

^{36}A2 Collaboration at MAMI,

^{37}A2 Collaboration at MAMI,

^{38}A2 Collaboration at MAMI,

^{39}A2 Collaboration at MAMI,

^{40}A2 Collaboration at MAMI,

^{41}A2 Collaboration at MAMI,

^{42}A2 Collaboration at MAMI,

^{43}A2 Collaboration at MAMI,

^{44}A2 Collaboration at MAMI,

^{45}A2 Collaboration at MAMI,

^{46}A2 Collaboration at MAMI,

^{47}A2 Collaboration at MAMI,

^{48}A2 Collaboration at MAMI,

^{49}A2 Collaboration at MAMI,

^{50}A2 Collaboration at MAMI,

^{51}A2 Collaboration at MAMI,

^{52}A2 Collaboration at MAMI,

^{53}A2 Collaboration at MAMI,

^{54}A2 Collaboration at MAMI,

^{55}A2 Collaboration at MAMI,

^{56}A2 Collaboration at MAMI,

^{57}A2 Collaboration at MAMI,

^{58}A2 Collaboration at MAMI,

^{59}A2 Collaboration at MAMI,

^{60}A2 Collaboration at MAMI,

^{61}A2 Collaboration at MAMI,

^{62}A2 Collaboration at MAMI,

^{63}A2 Collaboration at MAMI,

^{64}A2 Collaboration at MAMI,

^{65}A2 Collaboration at MAMI,

^{66}A2 Collaboration at MAMI,

^{67}A2 Collaboration at MAMI,

^{68}A2 Collaboration at MAMI,

^{69}A2 Collaboration at MAMI,

^{70}A2 Collaboration at MAMI,

^{71}A2 Collaboration at MAMI,

^{72}A2 Collaboration at MAMI,

^{73}A2 Collaboration at MAMI,

^{74}A2 Collaboration at MAMI,

^{75}A2 Collaboration at MAMI,

^{76}A2 Collaboration at MAMI,

^{77}A2 Collaboration at MAMI,

^{78}A2 Collaboration at MAMI,

^{79}A2 Collaboration at MAMI

A new measurement of the rare, doubly radiative decay eta->pi^0 gamma gamma was conducted with the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. New data on the dependence of the partial decay width, Gamma(eta->pi^0 gamma gamma), on the two-photon invariant mass squared, m^2(gamma gamma), as well as a new, more precise value for the decay width, Gamma(eta->pi^0 gamma gamma) = (0.33+/-0. Read More

**Authors:**M. Dieterle, I. Keshelashvili, J. Ahrens, J. R. M. Annand, H. J. Arends, K. Bantawa, P. A. Bartolome, R. Beck, V. Bekrenev, A. Braghieri, D. Branford, W. J. Briscoe, J. Brudvik, S. Cherepnya, B. Demissie, E. J. Downie, P. Drexler, L. V. Fil'kov, A. Fix, D. I. Glazier, D. Hamilton, E. Heid, D. Hornidge, D. Howdle, G. M. Huber, I. Jaegle, O. Jahn, T. C. Jude, A. Kaeser, V. L. Kashevarov, R. Kondratiev, M. Korolija, S. P. Kruglov, B. Krusche, A. Kulbardis, V. Lisin, K. Livingston, I. J. D. MacGregor, Y. Maghrbi, J. Mancell, D. M. Manley, Z. Marinides, M. Martinez, J. C. McGeorge, E. McNicoll, D. Mekterovic, V. Metag, S. Micanovic, D. G. Middleton, A. Mushkarenkov, B. M. K. Nefkens, A. Nikolaev, R. Novotny, M. Oberle, M. Ostrick, B. Oussena, P. Pedroni, F. Pheron, A. Polonski, S. N. Prakhov, J. Robinson, G. Rosner, T. Rostomyan, S. Schumann, M. H. Sikora, D. Sober, A. Starostin, I. Supek, M. Thiel, A. Thomas, M. Unverzagt, D. P. Watts, D. Werthmueller, L. Witthauer

**Category:**Nuclear Experiment

Precise angular distributions have been measured for the first time for the photoproduction of $\pi^{0}$-mesons off neutrons bound in the deuteron. The effects from nuclear Fermi motion have been eliminated by a complete kinematic reconstruction of the final state. The influence of final-state-interaction effects has been estimated by a comparison of the reaction cross section for quasi-free protons bound in the deuteron to the results for free protons and then applied as a correction to the quasi-free neutron data. Read More

**Authors:**M. Oberle, J. Ahrens, J. R. M. Annand, H. J. Arends, K. Bantawa, P. A. Bartolome, R. Beck, V. Bekrenev, H. Berghaeuser, A. Braghieri, D. Branford, W. J. Briscoe, J. Brudvik, S. Cherepnya, B. Demissie, M. Dieterle, E. J. Downie, P. Drexler, L. V. Fil'kov, A. Fix, D. I. Glazier, E. Heid, D. Hornidge, D. Howdle, G. M. Huber, O. Jahn, I. Jaegle, T. C. Jude, A. Kaeser, V. L. Kashevarov, I. Keshelashvili, R. Kondratiev, M. Korolija, S. P. Kruglov, B. Krusche, A. Kulbardis, V. Lisin, K. Livingston, I. J. D. MacGregor, Y. Maghrbi, J. Mancell, D. M. Manley, Z. Marinides, M. Martinez, J. C. McGeorge, E. McNicoll, D. Mekterovic, V. Metag, S. Micanovic, D. G. Middleton, A. Mushkarenkov, B. M. K. Nefkens, A. Nikolaev, R. Novotny, M. Ostrick, B. Oussena, P. Pedroni, F. Pheron, A. Polonski, S. N. Prakhov, J. Robinson, G. Rosner, T. Rostomyan, S. Schumann, M. H. Sikora, D. I. Sober, A. Starostin, I. Supek, M. Thiel, A. Thomas, M. Unverzagt, D. P. Watts, D. Werthmueller, L. Witthauer, F. Zehr

**Category:**Nuclear Experiment

Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz for the photoproduction of mixed-charge pion pairs in the reactions $\boldsymbol{\gamma}p\rightarrow n\pi^0\pi^+$ off free protons and $\boldsymbol{\gamma}d\rightarrow (p)p\pi^0\pi^-$ and $\boldsymbol{\gamma}d\rightarrow (n)n\pi^0\pi^+$ off quasi-free nucleons bound in the deuteron for incident photon energies up to 1.4 GeV. Circularly polarized photons were produced from bremsstrahlung of longitudinally polarized electrons and tagged with the Glasgow-Mainz magnetic spectrometer. Read More

**Authors:**L. Witthauer, D. Werthmueller, I. Keshelashvili, P. Aguar-Bartolome, J. Ahrens, J. R. M. Annand, H. J. Arends, K. Bantawa, R. Beck, V. Bekrenev, A. Braghieri, D. Branford, W. J. Briscoe, J. Brudvik, S. Cherepnya, B. Demissie, M. Dieterle, E. J. Downie, P. Drexler, L. V. Fil'kov, A. Fix, D. I. Glazier, D. Hamilton, E. Heid, D. Hornidge, D. Howdle, G. M. Huber, I. Jaegle, O. Jahn, T. C. Jude, A. Kaeser, V. L. Kashevarov, R. Kondratiev, M. Korolija, S. P. Kruglov, B. Krusche, A. Kulbardis, V. Lisin, K. Livingston, I. J. D. MacGregor, Y. Maghrbi, J. Mancell, D. M. Manley, Z. Marinides, M. Martinez, J. C. McGeorge, E. McNicoll, V. Metag, D. G. Middleton, A. Mushkarenkov, B. M. K. Nefkens, A. Nikolaev, R. Novotny, M. Oberle, M. Ostrick, B. Oussena, P. Pedroni, F. Pheron, A. Polonski, S. Prakhov, J. Robinson, G. Rosner, M. Rost, T. Rostomyan, S. Schumann, M. H. Sikora, D. Sober, A. Starostin, I. Supek, M. Thiel, A. Thomas, M. Unverzagt, D. P. Watts

**Category:**Nuclear Experiment

Quasi-free photoproduction of $\eta$-mesons has been measured off nucleons bound in $^3$He nuclei for incident photon energies from the threshold region up to 1.4 GeV. The experiment was performed at the tagged photon facility of the Mainz MAMI accelerator with an almost $4\pi$ covering electromagnetic calorimeter, combining the TAPS and Crystal Ball detectors. Read More

**Authors:**D. Werthmueller, L. Witthauer, I. Keshelashvili, P. Aguar-Bartolome, J. Ahrens, J. R. M. Annand, H. J. Arends, K. Bantawa, R. Beck, V. Bekrenev, A. Braghieri, D. Branford, W. J. Briscoe, J. Brudvik, S. Cherepnya, B. Demissie, M. Dieterle, E. J. Downie, P. Drexler, L. V. Fil'kov, A. Fix, D. I. Glazier, D. Hamilton, E. Heid, D. Hornidge, D. Howdle, G. M. Huber, I. Jaegle, O. Jahn, T. C. Jude, A. Kaeser, V. L. Kashevarov, R. Kondratiev, M. Korolija, S. P. Kruglov, B. Krusche, A. Kulbardis, V. Lisin, K. Livingston, I. J. D. MacGregor, Y. Maghrbi, J. Mancell, D. M. Manley, Z. Marinides, M. Martinez, J. C. McGeorge, E. F. McNicoll, V. Metag, D. G. Middleton, A. Mushkarenkov, B. M. K. Nefkens, A. Nikolaev, R. Novotny, M. Oberle, M. Ostrick, B. Oussena, P. Pedroni, F. Pheron, A. Polonski, S. N. Prakhov, J. Robinson, G. Rosner, T. Rostomyan, S. Schumann, M. H. Sikora, D. Sober, A. Starostin, I. Supek, M. Thiel, A. Thomas, M. Unverzagt, D. P. Watts

**Category:**Nuclear Experiment

The photoproduction of $\eta$-mesons off nucleons bound in $^2$H and $^3$He has been measured in coincidence with recoil protons and recoil neutrons for incident photon energies from threshold up to 1.4 GeV. The experiments were performed at the Mainz MAMI accelerator, using the Glasgow tagged photon facility. Read More

**Authors:**C. M. Tarbert, D. P. Watts, D. I. Glazier, P. Aguar, J. Ahrens, J. R. M. Annand, H. J. Arends, R. Beck, V. Bekrenev, B. Boillat, A. Braghieri, D. Branford, W. J. Briscoe, J. Brudvik, S. Cherepnya, R. Codling, E. J. Downie, K. Foehl, P. Grabmayr, R. Gregor, E. Heid, D. Hornidge, O. Jahn, V. L. Kashevarov, A. Knezevic, R. Kondratiev, M. Korolija, M. Kotulla, D. Krambrich, B. Krusche, M. Lang, V. Lisin, K. Livingston, S. Lugert, I. J. D. MacGregor, D. M. Manley, M. Martinez, J. C. McGeorge, D. Mekterovic, V. Metag, B. M. K. Nefkens, A. Nikolaev, R. Novotny, R. O. Owens, P. Pedroni, A. Polonski, S. N. Prakhov, J. W. Price, G. Rosner, M. Rost, T. Rostomyan, S. Schadmand, S. Schumann, D. Sober, A. Starostin, I. Supek, A. Thomas, M. Unverzagt, Th. Walcher, F. Zehr

Information on the size and shape of the neutron skin on $^{208}$Pb has been extracted from coherent pion photoproduction cross sections measured using the Crystal Ball together with the Glasgow tagger at the MAMI electron beam facility. On exploitation of an interpolated fit of a theoretical model to the measured cross sections the half-height radius and diffuseness of the neutron distribution are found to be 6.70$\pm 0. Read More

We generalize the classical Post correspondence problem ($\mathbf{PCP}_n$) and its non-homogeneous variation ($\mathbf{GPCP}_n$) to non-commutative groups and study the computational complexity of these new problems. We observe that $\mathbf{PCP}_n$ is closely related to the equalizer problem in groups, while $\mathbf{GPCP}_n$ is connected to the double twisted conjugacy problem for endomorphisms. Furthermore, it is shown that one of the strongest forms of the word problem in a group $G$ (we call it the {\em hereditary word problem}) can be reduced to $\mathbf{GPCP}_n$ in $G$ in polynomial time. Read More

**Authors:**D. P. Watts, D. I. Glazier, P. Aguar-BartolomÃ©\, L. K. Akasoy, J. R. M. Annand, H. J. Arends, K. Bantawa, R. Beck, V. S. Bekrenev, H. BerghÃ¤user, A. Braghieri, D. Branford, W. J. Briscoe, J. Brudvik, S. Cherepnya, R. F. B. Codling, B. T. Demissie, E. J. Downie, P. Drexler, L. V. Fil'kov, B. Freehart, R. Gregor, D. Hamilton, E. Heid, D. Hornidge, I. Jaegle, O. Jahn, T. C. Jude, V. L. Kashevarov, I. Keshelashvili, R. Kondratiev, M. Korolija, M. Kotulla, A. A. Koulbardis, S. P. Kruglov, B. Krusche, V. Lisin, K. Livingston, I. J. D. MacGregor, Y. Maghrbi, D. M. Manley, Z. Marinides, M. Martinez, J. C. McGeorge, B. McKinnon, E. F. McNicoll, D. Mekterovic, V. Metag, S. Micanovic, D. G. Middleton, A. Mushkarenkov, B. M. K. Nefkens, A. Nikolaev, R. Novotny, M. Ostrick, P. B. Otte, B. Oussena, P. Pedroni, F. Pheron, A. Polonski, S. Prakhov, J. Robinson, G. Rosner, T. Rostomyan, S. Schumann, D. I. Sober, A. Starostin, I. I. Strakovsky, I. M. Suarez, I. Supek, M. Thiel, A. Thomas, M. Unverzagt, D. WerthmÃ¼ller, R. L. Workman, I. Zamboni, F. Zehr

**Category:**Nuclear Experiment

We report the first large-acceptance measurement of polarization transfer
from a polarized photon beam to a recoiling nucleon, pioneering a novel
polarimetry technique with wide application to future nuclear and hadronic
physics experiments. The commissioning measurement of polarization transfer in
the $^{1}H$($\vec{\gamma}$,$\vec{p}$)$\pi^{0}$ reaction in the range
$0.4

**Authors:**P. Aguar-BartolomÃ©

^{1}, J. R. M. Annand

^{2}, H. J. Arends

^{3}, K. Bantawa

^{4}, R. Beck

^{5}, V. Bekrenev

^{6}, H. BerghÃ¤user

^{7}, A. Braghieri

^{8}, W. J. Briscoe

^{9}, J. Brudvik

^{10}, S. Cherepnya

^{11}, R. F. B. Codling

^{12}, C. Collicott

^{13}, S. Costanza

^{14}, A. Denig

^{15}, E. J. Downie

^{16}, P. Drexler

^{17}, L. V. Fil'kov

^{18}, A. Fix

^{19}, D. I. Glazier

^{20}, R. Gregor

^{21}, D. J. Hamilton

^{22}, E. Heid

^{23}, D. Hornidge

^{24}, L. Isaksson

^{25}, I. Jaegle

^{26}, O. Jahn

^{27}, T. C. Jude

^{28}, V. L. Kashevarov

^{29}, I. Keshelashvili

^{30}, R. Kondratiev

^{31}, M. Korolija

^{32}, M. Kotulla

^{33}, A. Koulbardis

^{34}, S. Kruglov

^{35}, B. Krusche

^{36}, V. Lisin

^{37}, K. Livingston

^{38}, I. J. D. MacGregor

^{39}, Y. Maghrbi

^{40}, D. M. Manley

^{41}, P. Masjuan

^{42}, J. C. McGeorge

^{43}, E. F. McNicoll

^{44}, D. Mekterovic

^{45}, V. Metag

^{46}, A. Mushkarenkov

^{47}, B. M. K. Nefkens

^{48}, A. Nikolaev

^{49}, R. Novotny

^{50}, H. Ortega

^{51}, M. Ostrick

^{52}, P. Ott

^{53}, P. B. Otte

^{54}, B. Oussena

^{55}, P. Pedroni

^{56}, F. Pheron

^{57}, A. Polonski

^{58}, S. Prakhov

^{59}, J. Robinson

^{60}, G. Rosner

^{61}, T. Rostomyan

^{62}, S. Schumann

^{63}, M. H. Sikora

^{64}, D. I. Sober

^{65}, A. Starostin

^{66}, I. I. Strakovsky

^{67}, I. M. Suarez

^{68}, I. Supek

^{69}, C. M. Tarbert

^{70}, M. Thiel

^{71}, A. Thomas

^{72}, M. Unverzagt

^{73}, D. P. Watts

^{74}, D. WerthmÃ¼ller

^{75}, F. Zehr.

^{76}

**Affiliations:**

^{1}A2 Collaboration at MAMI,

^{2}A2 Collaboration at MAMI,

^{3}A2 Collaboration at MAMI,

^{4}A2 Collaboration at MAMI,

^{5}A2 Collaboration at MAMI,

^{6}A2 Collaboration at MAMI,

^{7}A2 Collaboration at MAMI,

^{8}A2 Collaboration at MAMI,

^{9}A2 Collaboration at MAMI,

^{10}A2 Collaboration at MAMI,

^{11}A2 Collaboration at MAMI,

^{12}A2 Collaboration at MAMI,

^{13}A2 Collaboration at MAMI,

^{14}A2 Collaboration at MAMI,

^{15}A2 Collaboration at MAMI,

^{16}A2 Collaboration at MAMI,

^{17}A2 Collaboration at MAMI,

^{18}A2 Collaboration at MAMI,

^{19}A2 Collaboration at MAMI,

^{20}A2 Collaboration at MAMI,

^{21}A2 Collaboration at MAMI,

^{22}A2 Collaboration at MAMI,

^{23}A2 Collaboration at MAMI,

^{24}A2 Collaboration at MAMI,

^{25}A2 Collaboration at MAMI,

^{26}A2 Collaboration at MAMI,

^{27}A2 Collaboration at MAMI,

^{28}A2 Collaboration at MAMI,

^{29}A2 Collaboration at MAMI,

^{30}A2 Collaboration at MAMI,

^{31}A2 Collaboration at MAMI,

^{32}A2 Collaboration at MAMI,

^{33}A2 Collaboration at MAMI,

^{34}A2 Collaboration at MAMI,

^{35}A2 Collaboration at MAMI,

^{36}A2 Collaboration at MAMI,

^{37}A2 Collaboration at MAMI,

^{38}A2 Collaboration at MAMI,

^{39}A2 Collaboration at MAMI,

^{40}A2 Collaboration at MAMI,

^{41}A2 Collaboration at MAMI,

^{42}A2 Collaboration at MAMI,

^{43}A2 Collaboration at MAMI,

^{44}A2 Collaboration at MAMI,

^{45}A2 Collaboration at MAMI,

^{46}A2 Collaboration at MAMI,

^{47}A2 Collaboration at MAMI,

^{48}A2 Collaboration at MAMI,

^{49}A2 Collaboration at MAMI,

^{50}A2 Collaboration at MAMI,

^{51}A2 Collaboration at MAMI,

^{52}A2 Collaboration at MAMI,

^{53}A2 Collaboration at MAMI,

^{54}A2 Collaboration at MAMI,

^{55}A2 Collaboration at MAMI,

^{56}A2 Collaboration at MAMI,

^{57}A2 Collaboration at MAMI,

^{58}A2 Collaboration at MAMI,

^{59}A2 Collaboration at MAMI,

^{60}A2 Collaboration at MAMI,

^{61}A2 Collaboration at MAMI,

^{62}A2 Collaboration at MAMI,

^{63}A2 Collaboration at MAMI,

^{64}A2 Collaboration at MAMI,

^{65}A2 Collaboration at MAMI,

^{66}A2 Collaboration at MAMI,

^{67}A2 Collaboration at MAMI,

^{68}A2 Collaboration at MAMI,

^{69}A2 Collaboration at MAMI,

^{70}A2 Collaboration at MAMI,

^{71}A2 Collaboration at MAMI,

^{72}A2 Collaboration at MAMI,

^{73}A2 Collaboration at MAMI,

^{74}A2 Collaboration at MAMI,

^{75}A2 Collaboration at MAMI,

^{76}A2 Collaboration at MAMI

The Dalitz decay eta -> e^+ e^- gamma has been measured in the gamma p -> eta p reaction with the Crystal Ball and TAPS multiphoton spectrometers, together with the photon tagging facility at the Mainz Microtron MAMI. The experimental statistic used in this work is one order of magnitude greater than in any previous measurement of eta -> e^+ e^- gamma. The value obtained for the slope parameter 1/Lambda^2 of the eta transition form factor, 1/Lambda^2 = (1. Read More

**Authors:**T. C. Jude, D. I. Glazier, D. P. Watts, P. Aguar-Bartolome, L. K. Akasoy, J. R. M. Annand, H. J. Arends, K. Bantawa, R. Beck, V. S. Bekrenev, H. Berghauser, A. Braghieri, D. Branford, W. J. Briscoe, J. Brudvik, S. Cherepnya, B. T. Demissie, M. Dieterle, E. J. Downie, L. V. Fil'kov, R. Gregor, E. Heid, D. Hornidge, I. Jaegle, O. Jahn, V. L. Kashevarov, I. Keshelashvili, R. Kondratiev, M. Korolija, A. A. Koulbardis, S. P. Kruglov, B. Krusche, V. Lisin, K. Livingston, I. J. D. MacGregor, Y. Maghrbi, D. M. Manley, Z. Marinides, T. Mart, M. Martinez, J. C. McGeorge, E. F. McNicoll, D. G. Middleton, A. Mushkarenkov, B. M. K. Nefkens, A. Nikolaev, V. A. Nikonov, M. Oberle, M. Ostrick, P. B. Otte, B. Oussena, P. Pedroni, F. Pheron, A. Polonski, S. Prakhov, J. Robinson, G. Rosner, T. Rostomyan, A. V. Sarantsev, S. Schumann, M. H. Sikora, D. I. Sober, A. Starostin, I. Strakovsky, I. M. Suarez, I. Supek, M. Thiel, A. Thomas, M. Unverzagt, D. Werthmueller, L. Witthauer, F. Zehr

**Category:**Nuclear Experiment

Measurements of $\gamma p \rightarrow K^{+} \Lambda$ and $\gamma p \rightarrow K^{+} \Sigma^0$ cross-sections have been obtained with the photon tagging facility and the Crystal Ball calorimeter at MAMI-C. The measurement uses a novel $K^+$ meson identification technique in which the weak decay products are characterized using the energy and timing characteristics of the energy deposit in the calorimeter, a method that has the potential to be applied at many other facilities. The fine center-of-mass energy ($W$) resolution and statistical accuracy of the new data results in a significant impact on partial wave analyses aiming to better establish the excitation spectrum of the nucleon. Read More

This work explores the structure of Poincare-Lindstedt perturbation series in Deprit operator formalism and establishes its connection to Kato resolvent expansion. A discussion of invariant definitions for averaging and integrating perturbation operators and their canonical identities reveals a regular pattern in a Deprit generator. The pattern was explained using Kato series and the relation of perturbation operators to Laurent coefficients for the resolvent of Liouville operator. Read More

The study of the interaction potential between static charges within Monte-Carlo simulation of graphene is carried out. The numerical simulations are performed in the effective lattice field theory with noncompact $3 + 1$-dimensional Abelian lattice gauge fields and $2 + 1$-dimensional staggered lattice fermions. It is shown that for all considered temperatures the interaction can be well described by the Debye screened potential created by two-dimensional electron-hole excitations. Read More

**Authors:**P. Aguar-BartolomÃ©

^{1}, J. R. M. Annand

^{2}, H. J. Arends

^{3}, K. Bantawa

^{4}, R. Beck

^{5}, V. Bekrenev

^{6}, H. BerghÃ¤user

^{7}, A. Braghieri

^{8}, W. J. Briscoe

^{9}, J. Brudvik

^{10}, S. Cherepnya

^{11}, R. F. B. Codling

^{12}, C. Collicott

^{13}, B. Demissie

^{14}, M. Dieterle

^{15}, E. J. Downie

^{16}, P. Drexler

^{17}, L. V. Fil'kov

^{18}, A. Fix

^{19}, D. I. Glazier

^{20}, R. Gregor

^{21}, D. Hamilton

^{22}, E. Heid

^{23}, D. Hornidge

^{24}, D. Howdle

^{25}, L. Isaksson

^{26}, I. Jaegle

^{27}, O. Jahn

^{28}, T. C. Jude

^{29}, V. L. Kashevarov

^{30}, I. Keshelashvili

^{31}, R. Kondratiev

^{32}, M. Korolija

^{33}, M. Kotulla

^{34}, A. Koulbardis

^{35}, S. Kruglov

^{36}, B. Krusche

^{37}, V. Lisin

^{38}, K. Livingston

^{39}, I. J. D. MacGregor

^{40}, Y. Maghrbi

^{41}, J. Mancel

^{42}, D. M. Manley

^{43}, E. F. McNicoll

^{44}, D. Mekterovic

^{45}, V. Metag

^{46}, A. Mushkarenkov

^{47}, B. M. K. Nefkens

^{48}, A. Nikolaev

^{49}, R. Novotny

^{50}, M. Oberle

^{51}, H. Ortega

^{52}, M. Ostrick

^{53}, P. Ott

^{54}, P. B. Otte

^{55}, B. Oussena

^{56}, P. Pedroni

^{57}, F. Pheron

^{58}, A. Polonski

^{59}, S. Prakhov

^{60}, J. Robinson

^{61}, G. Rosner

^{62}, T. Rostomyan

^{63}, S. Schumann

^{64}, M. H. Sikora

^{65}, D. I. Sober

^{66}, A. Starostin

^{67}, I. I. Strakovsky

^{68}, I. M. Suarez

^{69}, I. Supek

^{70}, C. M. Tarbert

^{71}, M. Thiel

^{72}, A. Thomas

^{73}, M. Unverzagt

^{74}, D. P. Watts

^{75}, D. WerthmÃ¼ller

^{76}, L. Witthauer

^{77}, F. Zehr.

^{78}

**Affiliations:**

^{1}A2 Collaboration at MAMI,

^{2}A2 Collaboration at MAMI,

^{3}A2 Collaboration at MAMI,

^{4}A2 Collaboration at MAMI,

^{5}A2 Collaboration at MAMI,

^{6}A2 Collaboration at MAMI,

^{7}A2 Collaboration at MAMI,

^{8}A2 Collaboration at MAMI,

^{9}A2 Collaboration at MAMI,

^{10}A2 Collaboration at MAMI,

^{11}A2 Collaboration at MAMI,

^{12}A2 Collaboration at MAMI,

^{13}A2 Collaboration at MAMI,

^{14}A2 Collaboration at MAMI,

^{15}A2 Collaboration at MAMI,

^{16}A2 Collaboration at MAMI,

^{17}A2 Collaboration at MAMI,

^{18}A2 Collaboration at MAMI,

^{19}A2 Collaboration at MAMI,

^{20}A2 Collaboration at MAMI,

^{21}A2 Collaboration at MAMI,

^{22}A2 Collaboration at MAMI,

^{23}A2 Collaboration at MAMI,

^{24}A2 Collaboration at MAMI,

^{25}A2 Collaboration at MAMI,

^{26}A2 Collaboration at MAMI,

^{27}A2 Collaboration at MAMI,

^{28}A2 Collaboration at MAMI,

^{29}A2 Collaboration at MAMI,

^{30}A2 Collaboration at MAMI,

^{31}A2 Collaboration at MAMI,

^{32}A2 Collaboration at MAMI,

^{33}A2 Collaboration at MAMI,

^{34}A2 Collaboration at MAMI,

^{35}A2 Collaboration at MAMI,

^{36}A2 Collaboration at MAMI,

^{37}A2 Collaboration at MAMI,

^{38}A2 Collaboration at MAMI,

^{39}A2 Collaboration at MAMI,

^{40}A2 Collaboration at MAMI,

^{41}A2 Collaboration at MAMI,

^{42}A2 Collaboration at MAMI,

^{43}A2 Collaboration at MAMI,

^{44}A2 Collaboration at MAMI,

^{45}A2 Collaboration at MAMI,

^{46}A2 Collaboration at MAMI,

^{47}A2 Collaboration at MAMI,

^{48}A2 Collaboration at MAMI,

^{49}A2 Collaboration at MAMI,

^{50}A2 Collaboration at MAMI,

^{51}A2 Collaboration at MAMI,

^{52}A2 Collaboration at MAMI,

^{53}A2 Collaboration at MAMI,

^{54}A2 Collaboration at MAMI,

^{55}A2 Collaboration at MAMI,

^{56}A2 Collaboration at MAMI,

^{57}A2 Collaboration at MAMI,

^{58}A2 Collaboration at MAMI,

^{59}A2 Collaboration at MAMI,

^{60}A2 Collaboration at MAMI,

^{61}A2 Collaboration at MAMI,

^{62}A2 Collaboration at MAMI,

^{63}A2 Collaboration at MAMI,

^{64}A2 Collaboration at MAMI,

^{65}A2 Collaboration at MAMI,

^{66}A2 Collaboration at MAMI,

^{67}A2 Collaboration at MAMI,

^{68}A2 Collaboration at MAMI,

^{69}A2 Collaboration at MAMI,

^{70}A2 Collaboration at MAMI,

^{71}A2 Collaboration at MAMI,

^{72}A2 Collaboration at MAMI,

^{73}A2 Collaboration at MAMI,

^{74}A2 Collaboration at MAMI,

^{75}A2 Collaboration at MAMI,

^{76}A2 Collaboration at MAMI,

^{77}A2 Collaboration at MAMI,

^{78}A2 Collaboration at MAMI

The g p -> K^0 Sigma^+ reaction has been measured from threshold to Eg=1.45 GeV (W_cm=1.9 GeV) using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. Read More