N. Akopov

N. Akopov
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High Energy Physics - Experiment (23)
 
High Energy Physics - Phenomenology (12)
 
Nuclear Experiment (9)
 
Physics - Instrumentation and Detectors (3)
 
High Energy Physics - Lattice (2)
 
Physics - Accelerator Physics (2)
 
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Publications Authored By N. Akopov

Exclusive $\rho^0$-meson electroproduction is studied by the HERMES experiment, using the 27.6 GeV longitudinally polarized electron/positron beam of HERA and a transversely polarized hydrogen target, in the kinematic region 1.0 GeV$^2$Read More

Hard exclusive electroproduction of $\omega$ mesons is studied with the HERMES spectrometer at the DESY laboratory by scattering 27.6 GeV positron and electron beams off a transversely polarized hydrogen target. The amplitudes of five azimuthal modulations of the single-spin asymmetry of the cross section with respect to the transverse proton polarization are measured. Read More

2015May
Authors: HERMES Collaboration, A. Airapetian, N. Akopov, Z. Akopov, E. C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetisyan, S. Belostotski, N. Bianchi, H. P. Blok, A. Borissov, V. Bryzgalov, J. Burns, M. Capiluppi, G. P. Capitani, E. Cisbani, G. Ciullo, M. Contalbrigo, P. F. Dalpiaz, W. Deconinck, R. De Leo, E. De Sanctis, M. Diefenthaler, P. Di Nezza, M. Düren, G. Elbakian, F. Ellinghaus, E. Etzelmüller, R. Fabbri, A. Fantoni, L. Felawka, S. Frullani, G. Gapienko, V. Gapienko, J. Garay García, F. Garibaldi, G. Gavrilov, V. Gharibyan, F. Giordano, S. Gliske, M. Hartig, D. Hasch, Y. Holler, I. Hristova, Y. Imazu, A. Ivanilov, H. E. Jackson, S. Joosten, R. Kaiser, G. Karyan, T. Keri, E. Kinney, A. Kisselev, V. Korotkov, V. Kozlov, P. Kravchenko, V. G. Krivokhijine, L. Lagamba, L. Lapikás, I. Lehmann, P. Lenisa, A. López Ruiz, W. Lorenzon, X. -G. Lu, B. -Q. Ma, D. Mahon, N. C. R. Makins, Y. Mao, B. Marianski, A. Martinez de la Ossa, H. Marukyan, Y. Miyachi, A. Movsisyan, M. Murray, A. Mussgiller, E. Nappi, Y. Naryshkin, A. Nass, M. Negodaev, W. -D. Nowak, L. L. Pappalardo, R. Perez-Benito, A. Petrosyan, P. E. Reimer, A. R. Reolon, C. Riedl, K. Rith, G. Rosner, A. Rostomyan, J. Rubin, D. Ryckbosch, Y. Salomatin, A. Schäfer, G. Schnell, B. Seitz, T. -A. Shibata, V. Shutov, M. Stahl, M. Stancari, M. Statera, J. J. M. Steijger, S. Taroian, A. Terkulov, R. Truty, A. Trzcinski, M. Tytgat, Y. Van Haarlem, C. Van Hulse, D. Veretennikov, V. Vikhrov, I. Vilardi, S. Wang, S. Yaschenko, Z. Ye, S. Yen, B. Zihlmann, P. Zupranski

Bose-Einstein correlations of like-sign charged hadrons produced in deep-inelastic electron and positron scattering are studied in the HERMES experiment using nuclear targets of $^1$H, $^2$H, $^3$He, $^4$He, N, Ne, Kr, and Xe. A Gaussian approach is used to parametrize a two-particle correlation function determined from events with at least two charged hadrons of the same sign charge. This correlation function is compared to two different empirical distributions that do not include the Bose-Einstein correlations. Read More

The earlier search at HERMES for narrow baryon states excited in quasi-real photoproduction, decaying through the channel $pK_S^0\rightarrow p\pi^+\pi^-$, has been extended with improved decay-particle reconstruction, more advanced particle identification, and increased event samples. The structure observed earlier at an invariant mass of 1528 MeV shifts to 1522 MeV and the statistical significance drops to about 2$\sigma$ for data taken with a deuterium target. The number of events above background is $68_{-31}^{+98}\text{(stat)}\pm13\text{(sys)}$. Read More

2014Jul

Exclusive electroproduction of $\omega$ mesons on unpolarized hydrogen and deuterium targets is studied in the kinematic region of Q$^2$>1.0 GeV$^2$, 3.0 GeV < W < 6. Read More

2014Jun
Authors: The HERMES Collaboration, A. Airapetian, N. Akopov, Z. Akopov, E. C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetisyan, S. Belostotski, N. Bianchi, H. P. Blok, A. Borissov, J. Bowles, I. Brodski, V. Bryzgalov, J. Burns, M. Capiluppi, G. P. Capitani, E. Cisbani, G. Ciullo, M. Contalbrigo, P. F. Dalpiaz, W. Deconinck, R. De Leo, L. De Nardo, E. De Sanctis, M. Diefenthaler, P. Di Nezza, M. Düren, M. Ehrenfried, G. Elbakian, F. Ellinghaus, R. Fabbri, A. Fantoni, L. Felawka, S. Frullani, D. Gabbert, G. Gapienko, V. Gapienko, F. Garibaldi, G. Gavrilov, V. Gharibyan, F. Giordano, S. Gliske, M. Golembiovskaya, C. Hadjidakis, M. Hartig, D. Hasch, A. Hillenbrand, M. Hoek, Y. Holler, I. Hristova, Y. Imazu, A. Ivanilov, H. E. Jackson, H. S. Jo, S. Joosten, R. Kaiser, G. Karyan, T. Keri, E. Kinney, A. Kisselev, N. Kobayashi, V. Korotkov, V. Kozlov, P. Kravchenko, V. G. Krivokhijine, L. Lagamba, L. Lapikás, I. Lehmann, P. Lenisa, A. López Ruiz, W. Lorenzon, X. -G. Lu, B. -Q. Ma, D. Mahon, N. C. R. Makins, S. I. Manaenkov, Y. Mao, B. Marianski, A. Martinez de la Ossa, H. Marukyan, C. A. Miller, Y. Miyachi, A. Movsisyan, V. Muccifora, M. Murray, A. Mussgiller, E. Nappi, Y. Naryshkin, A. Nass, M. Negodaev, W. -D. Nowak, L. L. Pappalardo, R. Perez-Benito, P. E. Reimer, A. R. Reolon, C. Riedl, K. Rith, G. Rosner, A. Rostomyan, J. Rubin, D. Ryckbosch, Y. Salomatin, F. Sanftl, A. Schäfer, G. Schnell, K. P. Schüler, B. Seitz, T. -A. Shibata, V. Shutov, M. Stancari, M. Statera, E. Steffens, J. J. M. Steijger, J. Stewart, F. Stinzing, S. Taroian, A. Terkulov, R. Truty, A. Trzcinski, M. Tytgat, A. Vandenbroucke, Y. Van Haarlem, C. Van Hulse, D. Veretennikov, V. Vikhrov, I. Vilardi, S. Wang, S. Yaschenko, Z. Ye, W. Yu, V. Zagrebelnyy, D. Zeiler, B. Zihlmann, P. Zupranski

The transverse polarization of $\Lambda$ hyperons was measured in inclusive quasireal photoproduction for various target nuclei ranging from hydrogen to xenon. The data were obtained by the HERMES experiment at HERA using the 27.6 GeV lepton beam and nuclear gas targets internal to the lepton storage ring. Read More

2013Dec

An earlier extraction from the HERMES experiment of the polarization-averaged parton distribution of strange quarks in the nucleon has been reevaluated using final data on the multiplicities of charged kaons in semi-inclusive deep-inelastic scattering obtained with a kinematically more comprehensive method of correcting for experimental effects. General features of the distribution are confirmed, but the rise at low x is less pronounced than previously reported. Read More

The OLYMPUS experiment was designed to measure the ratio between the positron-proton and electron-proton elastic scattering cross sections, with the goal of determining the contribution of two-photon exchange to the elastic cross section. Two-photon exchange might resolve the discrepancy between measurements of the proton form factor ratio, $\mu_p G^p_E/G^p_M$, made using polarization techniques and those made in unpolarized experiments. OLYMPUS operated on the DORIS storage ring at DESY, alternating between 2. Read More

2013Oct
Authors: The HERMES Collaboration, A. Airapetian, N. Akopov, Z. Akopov, E. C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetisyan, S. Belostotski, N. Bianchi, H. P. Blok, A. Borissov, J. Bowles, V. Bryzgalov, J. Burns, M. Capiluppi, G. P. Capitani, E. Cisbani, G. Ciullo, M. Contalbrigo, P. F. Dalpiaz, W. Deconinck, R. De Leo, L. De Nardo, E. De Sanctis, M. Diefenthaler, P. Di Nezza, M. Düren, M. Ehrenfried, G. Elbakian, F. Ellinghaus, R. Fabbri, A. Fantoni, L. Felawka, S. Frullani, D. Gabbert, G. Gapienko, V. Gapienko, G. Gavrilov, V. Gharibyan, F. Giordano, S. Gliske, M. Golembiovskaya, C. Hadjidakis, M. Hartig, D. Hasch, A. Hillenbrand, M. Hoek, Y. Holler, I. Hristova, A. Ivanilov, H. E. Jackson, S. Joosten, R. Kaiser, G. Karyan, T. Keri, E. Kinney, A. Kisselev, V. Korotkov, V. Kozlov, P. Kravchenko, V. G. Krivokhijine, L. Lagamba, L. Lapikás, I. Lehmann, P. Lenisa, A. López Ruiz, W. Lorenzon, B. -Q. Ma, D. Mahon, N. C. R. Makins, S. I. Manaenkov, Y. Mao, B. Marianski, A. Martinez de la Ossa, H. Marukyan, C. A. Miller, Y. Miyachi, A. Movsisyan, V. Muccifora, M. Murray, A. Mussgiller, E. Nappi, Y. Naryshkin, A. Nass, M. Negodaev, W. -D. Nowak, L. L. Pappalardo, R. Perez-Benito, A. Petrosyan, M. Raithel, P. E. Reimer, A. R. Reolon, C. Riedl, K. Rith, G. Rosner, A. Rostomyan, J. Rubin, D. Ryckbosch, Y. Salomatin, F. Sanftl, A. Schäfer, G. Schnell, B. Seitz, T. -A. Shibata, V. Shutov, M. Stancari, M. Statera, E. Steffens, J. J. M. Steijger, J. Stewart, F. Stinzing, S. Taroian, A. Terkulov, R. Truty, A. Trzcinski, M. Tytgat, Y. Van Haarlem, C. Van Hulse, D. Veretennikov, V. Vikhrov, I. Vilardi, S. Wang, S. Yaschenko, Z. Ye, S. Yen, W. Yu, V. Zagrebelnyy, D. Zeiler, B. Zihlmann, P. Zupranski

Single-spin asymmetries were investigated in inclusive electroproduction of charged pions and kaons from transversely polarized protons at the HERMES experiment. The asymmetries were studied as a function of the azimuthal angle $\psi$ about the beam direction between the target-spin direction and the hadron production plane, the transverse hadron momentum relative to the direction of the incident beam, and the Feynman variable $x_F$. The $\sin(\psi)$ amplitudes are positive for positive pions and kaons, slightly negative for negative pions and consistent with zero for negative kaons, with particular transverse-momentum but weak $x_F$ dependences. Read More

2013Oct
Authors: The HERMES Collaboration, A. Airapetian, N. Akopov, E. C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetisyan, H. P. Blok, H. Böttcher, A. Borissov, J. Bowles, I. Brodski, V. Bryzgalov, J. Burns, G. P. Capitani, E. Cisbani, G. Ciullo, M. Contalbrigo, P. F. Dalpiaz, W. Deconinck, R. De Leo, E. De Sanctis, M. Diefenthaler, P. Di Nezza, M. Düren, M. Ehrenfried, G. Elbakian, F. Ellinghaus, E. Etzelmüller, R. Fabbri, S. Frullani, G. Gapienko, V. Gapienko, J. Garay García, F. Garibaldi, G. Gavrilov, V. Gharibyan, F. Giordano, S. Gliske, M. Hartig, D. Hasch, Y. Holler, I. Hristova, A. Ivanilov, H. E. Jackson, S. Joosten, R. Kaiser, G. Karyan, T. Keri, E. Kinney, A. Kisselev, V. Korotkov, V. Kozlov, P. Kravchenko, V. G. Krivokhijine, L. Lagamba, L. Lapikás, I. Lehmann, P. Lenisa, W. Lorenzon, X. -G. Lu, B. -Q. Ma, D. Mahon, N. C. R. Makins, S. I. Manaenkov, Y. Mao, B. Marianski, H. Marukyan, C. A. Miller, Y. Miyachi, A. Movsisyan, V. Muccifora, M. Murray, A. Mussgiller, Y. Naryshkin, A. Nass, M. Negodaev, W. -D. Nowak, L. L. Pappalardo, R. Perez-Benito, A. Petrosyan, P. E. Reimer, A. R. Reolon, C. Riedl, K. Rith, G. Rosner, A. Rostomyan, J. Rubin, D. Ryckbosch, Y. Salomatin, A. Schäfer, G. Schnell, B. Seitz, T. -A. Shibata, M. Stahl, M. Statera, E. Steffens, J. J. M. Steijger, J. Stewart, F. Stinzing, S. Taroian, A. Terkulov, R. Truty, A. Trzcinski, M. Tytgat, Y. Van Haarlem, C. Van Hulse, V. Vikhrov, I. Vilardi, S. Wang, S. Yaschenko, Z. Ye, S. Yen, V. Zagrebelnyy, B. Zihlmann, P. Zupranski

The beam-helicity asymmetry in associated electroproduction of real photons, $ep\to e\gamma \pi N$, in the $\Delta$(1232)-resonance region is measured using the longitudinally polarized HERA positron beam and an unpolarized hydrogen target. Azimuthal Fourier amplitudes of this asymmetry are extracted separately for two channels, $ep\to e\gamma \pi^0 p$ and $ep\to e\gamma \pi^+ n$, from a data set collected with a recoil detector. All asymmetry amplitudes are found to be consistent with zero. Read More

2012Dec
Authors: HERMES Collaboration, A. Airapetian, N. Akopov, Z. Akopov, E. C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetisyan, S. Belostotski, H. P. Blok, A. Borissov, J. Bowles, I. Brodski, V. Bryzgalov, J. Burns, M. Capiluppi, G. P. Capitani, E. Cisbani, G. Ciullo, M. Contalbrigo, P. F. Dalpiaz, W. Deconinck, R. De Leo, L. De Nardo, E. De Sanctis, M. Diefenthaler, P. Di Nezza, M. Düren, M. Ehrenfried, G. Elbakian, F. Ellinghaus, R. Fabbri, A. Fantoni, L. Felawka, S. Frullani, D. Gabbert, G. Gapienko, V. Gapienko, F. Garibaldi, G. Gavrilov, V. Gharibyan, F. Giordano, S. Gliske, M. Golembiovskaya, C. Hadjidakis, M. Hartig, D. Hasch, A. Hillenbrand, M. Hoek, Y. Holler, I. Hristova, Y. Imazu, A. Ivanilov, A. Izotov, H. E. Jackson, H. S. Jo, S. Joosten, R. Kaiser, G. Karyan, T. Keri, E. Kinney, A. Kisselev, N. Kobayashi, V. Korotkov, V. Kozlov, P. Kravchenko, V. G. Krivokhijine, L. Lagamba, L. Lapikás, I. Lehmann, P. Lenisa, A. López Ruiz, W. Lorenzon, B. -Q. Ma, D. Mahon, B. Maiheu, N. C. R. Makins, S. I. Manaenkov, L. Manfré, Y. Mao, B. Marianski, A. Martinez de la Ossa, H. Marukyan, C. A. Miller, Y. Miyachi, A. Movsisyan, M. Murray, A. Mussgiller, E. Nappi, Y. Naryshkin, A. Nass, M. Negodaev, W. -D. Nowak, L. L. Pappalardo, R. Perez-Benito, A. Petrosyan, M. Raithel, P. E. Reimer, A. R. Reolon, C. Riedl, K. Rith, G. Rosner, A. Rostomyan, J. Rubin, D. Ryckbosch, Y. Salomatin, F. Sanftl, A. Schäfer, G. Schnell, B. Seitz, T. -A. Shibata, V. Shutov, M. Stancari, M. Statera, E. Steffens, J. J. M. Steijger, J. Stewart, F. Stinzing, S. Taroian, A. Terkulov, R. Truty, A. Trzcinski, M. Tytgat, Y. Van Haarlem, C. Van Hulse, D. Veretennikov, I. Vilardi, C. Vogel, S. Wang, S. Yaschenko, Z. Ye, S. Yen, W. Yu, V. Zagrebelnyy, D. Zeiler, B. Zihlmann, P. Zupranski

Multiplicities in semi-inclusive deep-inelastic scattering are presented for each charge state of \pi^\pm and K^\pm mesons. The data were collected by the HERMES experiment at the HERA storage ring using 27.6 GeV electron and positron beams incident on a hydrogen or deuterium gas target. Read More

2012Jun
Authors: The HERMES Collaboration, A. Airapetian, N. Akopov, Z. Akopov, E. C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetisyan, S. Belostotski, H. P. Blok, A. Borissov, J. Bowles, I. Brodski, V. Bryzgalov, J. Burns, M. Capiluppi, G. P. Capitani, E. Cisbani, G. Ciullo, M. Contalbrigo, P. F. Dalpiaz, W. Deconinck, R. De Leo, L. De Nardo, E. De Sanctis, M. Diefenthaler, P. Di Nezza, M. Düren, M. Ehrenfried, G. Elbakian, F. Ellinghaus, E. Etzelmüller, R. Fabbri, A. Fantoni, L. Felawka, S. Frullani, G. Gapienko, V. Gapienko, F. Garibaldi, G. Gavrilov, V. Gharibyan, F. Giordano, S. Gliske, M. Golembiovskaya, I. M. Gregor, H. Guler, M. Hartig, D. Hasch, A. Hillenbrand, M. Hoek, Y. Holler, I. Hristova, A. Ivanilov, H. E. Jackson, H. S. Jo, S. Joosten, R. Kaiser, G. Karyan, T. Keri, E. Kinney, A. Kisselev, V. Korotkov, V. Kozlov, B. Krauss, P. Kravchenko, V. G. Krivokhijine, L. Lagamba, L. Lapikás, I. Lehmann, P. Lenisa, A. López Ruiz, W. Lorenzon, S. Lu, X. Lu, B. -Q. Ma, D. Mahon, N. C. R. Makins, S. I. Manaenkov, L. Manfré, Y. Mao, B. Marianski, A. Martinez de la Ossa, H. Marukyan, C. A. Miller, Y. Miyachi, A. Movsisyan, M. Murray, A. Mussgiller, E. Nappi, Y. Naryshkin, A. Nass, M. Negodaev, W. -D. Nowak, A. Osborne, L. L. Pappalardo, R. Perez-Benito, A. Petrosyan, P. E. Reimer, A. R. Reolon, C. Riedl, K. Rith, G. Rosner, A. Rostomyan, L. Rubacek, J. Rubin, D. Ryckbosch, A. Schäfer, G. Schnell, K. P. Schüler, B. Seitz, C. Shearer, T. -A. Shibata, V. Shutov, M. Stancari, M. Statera, J. J. M. Steijger, J. Stewart, S. Taroian, A. Terkulov, R. Truty, A. Trzcinski, M. Tytgat, Y. Van Haarlem, C. Van Hulse, D. Veretennikov, V. Vikhrov, I. Vilardi, S. Wang, S. Yaschenko, Z. Ye, S. Yen, V. Zagrebelnyy, D. Zeiler, B. Zihlmann, P. Zupranski

The beam-helicity asymmetry in exclusive electroproduction of real photons by the longitudinally polarized HERA positron beam scattering off an unpolarized hydrogen target is measured at HERMES. The asymmetry arises from deeply virtual Compton scattering and its interference with the Bethe--Heitler process. Azimuthal amplitudes of the beam-helicity asymmetry are extracted from a data sample consisting of $ep\rightarrow ep\gamma$ events with detection of all particles in the final state including the recoiling proton. Read More

2012Apr
Authors: HERMES Collaboration, A. Airapetian, N. Akopov, Z. Akopov, E. C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetisyan, S. Belostotski, H. P. Blok, A. Borissov, J. Bowles, V. Bryzgalov, J. Burns, M. Capiluppi, G. P. Capitani, G. Ciullo, M. Contalbrigo, P. F. Dalpiaz, W. Deconinck, R. De Leo, L. De Nardo, E. De Sanctis, M. Diefenthaler, P. Di Nezza, M. Düren, G. Elbakian, F. Ellinghaus, A. Fantoni, L. Felawka, S. Frullani, G. Gapienko, V. Gapienko, F. Garibaldi, G. Gavrilov, V. Gharibyan, F. Giordano, S. Gliske, M. Golembiovskaya, C. Hadjidakis, M. Hartig, D. Hasch, A. Hillenbrand, M. Hoek, Y. Holler, I. Hristova, Y. Imazu, A. Ivanilov, H. E. Jackson, H. S. Jo, S. Joosten, R. Kaiser, G. Karyan, T. Keri, E. Kinney, A. Kisselev, V. Korotkov, V. Kozlov, P. Kravchenko, V. G. Krivokhijine, L. Lagamba, L. Lapikás, I. Lehmann, P. Lenisa, A. López Ruiz, W. Lorenzon, B. -Q. Ma, D. Mahon, N. C. R. Makins, S. I. Manaenkov, L. Manfré, Y. Mao, B. Marianski, A. Martinez de la Ossa, H. Marukyan, C. A. Miller, Y. Miyachi, A. Movsisyan, M. Murray, E. Nappi, Y. Naryshkin, A. Nass, M. Negodaev, W. -D. Nowak, L. L. Pappalardo, R. Perez-Benito, A. Petrosyan, M. Raithel, P. E. Reimer, A. R. Reolon, C. Riedl, K. Rith, G. Rosner, A. Rostomyan, J. Rubin, D. Ryckbosch, Y. Salomatin, F. Sanftl, A. Schäfer, G. Schnell, K. P. Schüler, B. Seitz, T. -A. Shibata, M. Stancari, M. Statera, J. J. M. Steijger, J. Stewart, F. Stinzing, A. Terkulov, R. Truty, A. Trzcinski, M. Tytgat, A. Vandenbroucke, Y. Van Haarlem, C. Van Hulse, D. Veretennikov, V. Vikhrov, I. Vilardi, S. Wang, S. Yaschenko, Z. Ye, S. Yen, W. Yu, V. Zagrebelnyy, D. Zeiler, B. Zihlmann, P. Zupranski

The azimuthal cos{\phi} and cos2{\phi} modulations of the distribution of hadrons produced in unpolarized semi-inclusive deep-inelastic scattering of electrons and positrons off hydrogen and deuterium targets have been measured in the HERMES experiment. For the first time these modulations were determined in a four-dimensional kinematic space for positively and negatively charged pions and kaons separately, as well as for unidentified hadrons. These azimuthal dependences are sensitive to the transverse motion and polarization of the quarks within the nucleon via, e. Read More

2012Mar
Authors: The HERMES Collaboration, A. Airapetian, N. Akopov, Z. Akopov, E. C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetisyan, H. P. Blok, A. Borissov, J. Bowles, V. Bryzgalov, J. Burns, M. Capiluppi, G. P. Capitani, E. Cisbani, G. Ciullo, M. Contalbrigo, P. F. Dalpiaz, W. Deconinck, R. De Leo, L. De Nardo, E. De Sanctis, M. Diefenthaler, P. Di Nezza, M. Düren, M. Ehrenfried, G. Elbakian, F. Ellinghaus, A. Fantoni, L. Felawka, S. Frullani, D. Gabbert, G. Gapienko, V. Gapienko, F. Garibaldi, G. Gavrilov, F. Giordano, S. Gliske, M. Golembiovskaya, C. Hadjidakis, M. Hartig, D. Hasch, M. Hoek, Y. Holler, Y. Imazu, H. E. Jackson, H. S. Jo, R. Kaiser, G. Karyan, T. Keri, E. Kinney, A. Kisselev, N. Kobayashi, V. Korotkov, V. Kozlov, P. Kravchenko, V. G. Krivokhijine, L. Lagamba, L. Lapikás, I. Lehmann, P. Lenisa, W. Lorenzon, B. -Q. Ma, D. Mahon, N. C. R. Makins, S. I. Manaenkov, L. Manfré, Y. Mao, B. Marianski, A. Martinez de la Ossa, H. Marukyan, C. A. Miller, Y. Miyachi, A. Movsisyan, V. Muccifora, M. Murray, A. Mussgiller, E. Nappi, Y. Naryshkin, A. Nass, W. -D. Nowak, L. L. Pappalardo, R. Perez-Benito, A. Petrosyan, M. Raithel, P. E. Reimer, A. R. Reolon, C. Riedl, K. Rith, G. Rosner, A. Rostomyan, J. Rubin, D. Ryckbosch, Y. Salomatin, F. Sanftl, A. Schäfer, G. Schnell, K. P. Schüler, B. Seitz, T. -A. Shibata, V. Shutov, M. Stancari, M. Statera, E. Steffens, J. J. M. Steijger, J. Stewart, S. Taroian, A. Terkulov, R. Truty, A. Trzcinski, M. Tytgat, Y. Van Haarlem, C. Van Hulse, D. Veretennikov, V. Vikhrov, I. Vilardi, S. Wang, S. Yaschenko, Z. Ye, S. Yen, W. Yu, V. Zagrebelnyy, D. Zeiler, B. Zihlmann, P. Zupranski

Beam-helicity and beam-charge asymmetries in the hard exclusive leptoproduction of real photons from an unpolarised hydrogen target by a 27.6 GeV lepton beam are extracted from the HERMES data set of 2006-2007 using a missing-mass event selection technique. The asymmetry amplitudes extracted from this data set are more precise than those extracted from the earlier data set of 1996-2005 previously analysed in the same manner by HERMES. Read More

2011Dec
Authors: The HERMES Collaboration, A. Airapetian, N. Akopov, Z. Akopov, E. C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetisyan, S. Belostotski, N. Bianchi, H. P. Blok, A. Borissov, J. Bowles, V. Bryzgalov, J. Burns, M. Capiluppi, G. P. Capitani, E. Cisbani, G. Ciullo, M. Contalbrigo, P. F. Dalpiaz, W. Deconinck, R. De Leo, L. De Nardo, E. De Sanctis, M. Diefenthaler, P. Di Nezza, M. Düren, M. Ehrenfried, G. Elbakian, F. Ellinghaus, A. Fantoni, L. Felawka, S. Frullani, D. Gabbert, G. Gapienko, V. Gapienko, F. Garibaldi, G. Gavrilov, V. Gharibyan, F. Giordano, S. Gliske, M. Golembiovskaya, C. Hadjidakis, M. Hartig, D. Hasch, A. Hillenbrand, M. Hoek, Y. Holler, I. Hristova, Y. Imazu, A. Ivanilov, H. E. Jackson, H. S. Jo, S. Joosten, R. Kaiser, G. Karyan, T. Keri, E. Kinney, A. Kisselev, V. Korotkov, V. Kozlov, P. Kravchenko, V. G. Krivokhijine, L. Lagamba, L. Lapikás, I. Lehmann, P. Lenisa, A. López Ruiz, W. Lorenzon, B. -Q. Ma, D. Mahon, N. C. R. Makins, S. I. Manaenkov, L. Manfré, Y. Mao, B. Marianski, A. Martinez de la Ossa, H. Marukyan, C. A. Miller, Y. Miyachi, A. Movsisyan, V. Muccifora, M. Murray, A. Mussgiller, E. Nappi, Y. Naryshkin, A. Nass, M. Negodaev, W. -D. Nowak, L. L. Pappalardo, R. Perez-Benito, A. Petrosyan, P. E. Reimer, A. R. Reolon, C. Riedl, K. Rith, G. Rosner, A. Rostomyan, J. Rubin, D. Ryckbosch, Y. Salomatin, F. Sanftl, A. Schäfer, G. Schnell, K. P. Schüler, B. Seitz, T. -A. Shibata, V. Shutov, M. Stancari, M. Statera, E. Steffens, J. J. M. Steijger, J. Stewart, F. Stinzing, S. Taroian, A. Terkulov, R. Truty, A. Trzcinski, M. Tytgat, A. Vandenbroucke, Y. Van Haarlem, C. Van Hulse, D. Veretennikov, V. Vikhrov, I. Vilardi, S. Wang, S. Yaschenko, Z. Ye, S. Yen, V. Zagrebelnyy, D. Zeiler, B. Zihlmann, P. Zupranski

A measurement of the virtual-photon asymmetry A_2(x,Q^2) and of the spin-structure function g_2(x,Q^2) of the proton are presented for the kinematic range 0.004 < x < 0.9 and 0. Read More

2011Jul
Authors: HERMES Collaboration, A. Airapetian, N. Akopov, Z. Akopov, E. C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetisyan, S. Belostotski, N. Bianchi, H. P. Blok, A. Borissov, J. Bowles, I. Brodski, V. Bryzgalov, J. Burns, M. Capiluppi, G. P. Capitani, E. Cisbani, G. Ciullo, M. Contalbrigo, P. F. Dalpiaz, W. Deconinck, R. De Leo, L. De Nardo, E. De Sanctis, M. Diefenthaler, P. Di Nezza, M. Düren, M. Ehrenfried, G. Elbakian, F. Ellinghaus, R. Fabbri, A. Fantoni, L. Felawka, S. Frullani, G. Gapienko, V. Gapienko, G. Gavrilov, V. Gharibyan, F. Giordano, S. Gliske, M. Golembiovskaya, L. Grigoryan, C. Hadjidakis, M. Hartig, D. Hasch, A. Hillenbrand, M. Hoek, Y. Holler, I. Hristova, Y. Imazu, A. Ivanilov, H. E. Jackson, H. S. Jo, S. Joosten, R. Kaiser, G. Karyan, T. Keri, E. Kinney, A. Kisselev, N. Kobayashi, V. Korotkov, V. Kozlov, P. Kravchenko, V. G. Krivokhijine, L. Lagamba, L. Lapikás, I. Lehmann, P. Lenisa, A. López Ruiz, W. Lorenzon, X. -G. Lu, X. -R. Lu, B. -Q. Ma, D. Mahon, N. C. R. Makins, S. I. Manaenkov, L. Manfré, Y. Mao, B. Marianski, A. Martinez de la Ossa, H. Marukyan, C. A. Miller, Y. Miyachi, A. Movsisyan, V. Muccifora, M. Murray, A. Mussgiller, E. Nappi, Y. Naryshkin, A. Nass, M. Negodaev, W. -D. Nowak, L. L. Pappalardo, R. Perez-Benito, A. Petrosyan, M. Raithel, P. E. Reimer, A. R. Reolon, C. Riedl, K. Rith, G. Rosner, A. Rostomyan, J. Rubin, D. Ryckbosch, Y. Salomatin, F. Sanftl, A. Schäfer, G. Schnell, B. Seitz, T. -A. Shibata, V. Shutov, M. Stancari, M. Statera, E. Steffens, J. J. M. Steijger, J. Stewart, F. Stinzing, S. Taroian, R. Truty, A. Trzcinski, M. Tytgat, A. Vandenbroucke, Y. Van Haarlem, C. Van Hulse, D. Veretennikov, V. Vikhrov, I. Vilardi, C. Vogel, S. Wang, S. Yaschenko, Z. Ye, S. Yen, W. Yu, V. Zagrebelnyy, D. Zeiler, B. Zihlmann, P. Zupranski

Hadron multiplicities in semi-inclusive deep-inelastic scattering were measured on neon, krypton and xenon targets relative to deuterium at an electron(positron)-beam energy of 27.6 GeV at HERMES. These ratios were determined as a function of the virtual-photon energy nu, its virtuality Q2, the fractional hadron energy z and the transverse hadron momentum with respect to the virtual-photon direction pt . Read More

2011Jun
Authors: The HERMES Collaboration, A. Airapetian, N. Akopov, Z. Akopov, E. C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetisyan, S. Belostotski, N. Bianchi, H. P. Blok, A. Borissov, J. Bowles, I. Brodski, V. Bryzgalov, J. Burns, M. Capiluppi, G. P. Capitani, E. Cisbani, G. Ciullo, M. Contalbrigo, P. F. Dalpiaz, W. Deconinck, R. De Leo, L. De Nardo, E. De Sanctis, P. Di Nezza, M. Dueren, M. Ehrenfried, G. Elbakian, F. Ellinghaus, R. Fabbri, A. Fantoni, L. Felawka, S. Frullani, D. Gabbert, G. Gapienko, V. Gapienko, F. Garibaldi, G. Gavrilov, V. Gharibyan, F. Giordano, S. Gliske, M. Golembiovskaya, M. Hartig, D. Hasch, M. Hoek, Y. Holler, I. Hristova, Y. Imazu, A. Ivanilov, H. E. Jackson, H. S. Jo, S. Joosten, R. Kaiser, G. Karyan, T. Keri, E. Kinney, A. Kisselev, V. Korotkov, V. Kozlov, P. Kravchenko, V. G. Krivokhijine, L. Lagamba, L. Lapikas, I. Lehmann, P. Lenisa, A. Lopez Ruiz, W. Lorenzon, X. -G. Lu, X. -R. Lu, B. -Q. Ma, D. Mahon, N. C. R. Makins, S. I. Manaenkov, L. Manfre, Y. Mao, B. Marianski A. Martinez de la Ossa, H. Marukyan, C. A. Miller, Y. Miyachi, A. Movsisyan, M. Murray, A. Mussgiller, E. Nappi, Y. Naryshkin, A. Nass, M. Negodaev, W. -D. Nowak, L. L. Pappalardo, R. Perez-Benito, M. Raithel, P. E. Reimer, A. R. Reolon, C. Riedl, K. Rith, G. Rosner, A. Rostomyan, J. Rubin, D. Ryckbosch, Y. Salomatin, A. Schaefer, G. Schnell, K. P. Schueler, B. Seitz, T. -A. Shibata, V. Shutov, M. Stancari, M. Statera, E. Steffens, J. J. M. Steijger, F. Stinzing, S. Taroian, A. Terkulov, R. Truty, A. Trzcinski, M. Tytgat, Y. Van Haarlem, C. Van Hulse, D. Veretennikov, V. Vikhrov, I. Vilardi, S. Wang, S. Yaschenko, Z. Ye, S. Yen, V. Zagrebelnyy, D. Zeiler, B. Zihlmann, P. Zupranski

Double-spin asymmetries in exclusive electroproduction of real photons from a transversely polarized hydrogen target are measured with respect to the product of target polarization with beam helicity and beam charge, and with respect to the product of target polarization with beam helicity alone. The asymmetries arise from the deeply virtual Compton scattering process and its interference with the Bethe--Heitler process. They are related to the real part of the same combination of Compton form factors as that determining the previously published transverse target single-spin asymmetries through the imaginary part. Read More

2011Mar
Authors: The HERMES Collaboration, A. Airapetian, N. Akopov, Z. Akopov, E. C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetisyan, S. Belostotski, N. Bianchi, H. P. Blok, A. Borissov, J. Bowles, V. Bryzgalov, J. Burns, M. Capiluppi, G. P. Capitani, E. Cisbani, G. Ciullo, M. Contalbrigo, P. F. Dalpiaz, W. Deconinck, R. De Leo, L. De Nardo, E. De Sanctis, M. Diefenthaler, P. Di Nezza, M. Dueren, M. Ehrenfried, G. Elbakian, F. Ellinghaus, R. Fabbri, A. Fantoni, L. Felawka, S. Frullani, D. Gabbert, G. Gapienko, V. Gapienko, F. Garibaldi, G. Gavrilov, V. Gharibyan, F. Giordano, S. Gliske, M. Golembiovskaya, C. Hadjidakis, M. Hartig, D. Hasch, G. Hill, A. Hillenbrand, M. Hoek, Y. Holler, I. Hristova, Y. Imazu, A. Ivanilov, H. E. Jackson, H. S. Jo, S. Joosten, R. Kaiser, G. Karyan, T. Keri, E. Kinney, A. Kisselev, V. Korotkov, V. Kozlov, P. Kravchenko, V. G. Krivokhijine, L. Lagamba, R. Lamb, L. Lapikas, I. Lehmann, P. Lenisa, L. A. Linden-Levy, A. Lopez Ruiz, W. Lorenzon, X. -G. Lu, X. -R. Lu, B. -Q. Ma, D. Mahon, N. C. R. Makins, S. I. Manaenkov, L. Manfre, Y. Mao, B. Marianski, A. Martinez de la Ossa, H. Marukyan, C. A. Miller, Y. Miyachi, A. Movsisyan, V. Muccifora, M. Murray, A. Mussgiller, E. Nappi, Y. Naryshkin, A. Nass, M. Negodaev, W. -D. Nowak, L. L. Pappalardo, R. Perez-Benito, N. Pickert, M. Raithel, P. E. Reimer, A. R. Reolon, C. Riedl, K. Rith, G. Rosner, A. Rostomyan, J. Rubin, D. Ryckbosch, Y. Salomatin, F. Sanftl, A. Schaefer, G. Schnell, K. P. Schueler, B. Seitz, T. -A. Shibata, V. Shutov, M. Stancari, M. Statera, E. Steffens, J. J. M. Steijger, H. Stenzel, J. Stewart, F. Stinzing, S. Taroian, A. Trzcinski, M. Tytgat, A. Vandenbroucke, Y. Van Haarlem, C. Van Hulse, D. Veretennikov, V. Vikhrov, I. Vilardi, C. Vogel, S. Wang, S. Yaschenko, H. Ye, Z. Ye, S. Yen, W. Yu, D. Zeiler, B. Zihlmann, P. Zupranski

Results of inclusive measurements of inelastic electron and positron scattering from unpolarized protons and deuterons at the HERMES experiment are presented. The structure functions $F_2^p$ and $F_2^d$ are determined using a parameterization of existing data for the longitudinal-to-transverse virtual-photon absorption cross-section ratio. The HERMES results provide data in the ranges $0. Read More

2010Dec
Authors: The HERMES Collaboration, A. Airapetian, N. Akopov, Z. Akopov, E. C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetisyan, S. Belostotski, N. Bianchi, H. P. Blok, A. Borissov, J. Bowles, V. Bryzgalov, J. Burns, M. Capiluppi, G. P. Capitani, E. Cisbani, G. Ciullo, M. Contalbrigo, P. F. Dalpiaz, W. Deconinck, R. De Leo, L. De Nardo, E. De Sanctis, M. Diefenthaler, P. Di Nezza, M. Dueren, M. Ehrenfried, G. Elbakian, F. Ellinghaus, R. Fabbri, A. Fantoni, L. Felawka, S. Frullani, D. Gabbert, G. Gapienko, V. Gapienko, F. Garibaldi, G. Gavrilov, V. Gharibyan, F. Giordano, S. Gliske, M. Golembiovskaya, C. Hadjidakis, M. Hartig, D. Hasch, G. Hill, A. Hillenbrand, M. Hoek, Y. Holler, I. Hristova, Y. Imazu, A. Ivanilov, H. E. Jackson, H. S. Jo, S. Joosten, R. Kaiser, G. Karyan, T. Keri, E. Kinney, A. Kisselev, N. Kobayashi, V. Korotkov, V. Kozlov, P. Kravchenko, V. G. Krivokhijine, L. Lagamba, R. Lamb, L. Lapikas, I. Lehmann, P. Lenisa, L. A. Linden-Levy, A. Lopez Ruiz, W. Lorenzon, X. -G. Lu, X. -R. Lu, B. -Q. Ma, D. Mahon, N. C. R. Makins, S. I. Manaenkov, L. Manfre, Y. Mao, B. Marianski, A. Martinez de la Ossa, H. Marukyan, C. A. Miller, Y. Miyachi, A. Movsisyan, V. Muccifora, M. Murray, A. Mussgiller, E. Nappi, Y. Naryshkin, A. Nass, M. Negodaev, W. -D. Nowak, L. L. Pappalardo, R. Perez-Benito, N. Pickert, P. E. Reimer, A. R. Reolon, C. Riedl, K. Rith, G. Rosner, A. Rostomyan, J. Rubin, D. Ryckbosch, Y. Salomatin, F. Sanftl, A. Schaefer, G. Schnell, K. P. Schueler, B. Seitz, T. -A. Shibata, V. Shutov, M. Stancari, M. Statera, E. Steffens, J. J. M. Steijger, F. Stinzing, S. Taroian, A. Terkulov, A. Trzcinski, M. Tytgat, A. Vandenbroucke, Y. Van Haarlem, C. Van Hulse, D. Veretennikov, V. Vikhrov, I. Vilardi, S. Wang, S. Yaschenko, S. Yen, W. Yu, B. Zihlmann, P. Zupranski

Exclusive rho^0-meson electroproduction is studied in the HERMES experiment, using a 27.6 GeV longitudinally polarized electron/positron beam and unpolarized hydrogen and deuterium targets in the kinematic region 0.5 GeV^2 < Q^2 < 7. Read More

2010Aug
Authors: The HERMES Collaboration, A. Airapetian, N. Akopov, Z. Akopov, E. C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetisyan, S. Belostotski, N. Bianchi, H. P. Blok, A. Borissov, J. Bowles, I. Brodski, V. Bryzgalov, J. Burns, M. Capiluppi, G. P. Capitani, E. Cisbani, G. Ciullo, M. Contalbrigo, P. F. Dalpiaz, W. Deconinck, R. De Leo, L. De Nardo, E. De Sanctis, M. Diefenthaler, P. Di Nezza, M. Dueren, M. Ehrenfried, G. Elbakian, F. Ellinghaus, A. Fantoni, L. Felawka, S. Frullani, D. Gabbert, G. Gapienko, V. Gapienko, F. Garibaldi, G. Gavrilov, V. Gharibyan, F. Giordano, S. Gliske, M. Golembiovskaya, C. Hadjidakis, M. Hartig, D. Hasch, G. Hill, A. Hillenbrand, M. Hoek, Y. Holler, I. Hristova, Y. Imazu, A. Ivanilov, H. E. Jackson, A. Jgoun, H. S. Jo, S. Joosten, R. Kaiser, G. Karyan, T. Keri, E. Kinney, A. Kisselev, N. Kobayashi, V. Korotkov, V. Kozlov, B. Krauss, P. Kravchenko, V. G. Krivokhijine, L. Lagamba, R. Lamb, L. Lapikas, I. Lehmann, P. Lenisa, L. A. Linden-Levy, A. Lopez Ruiz, W. Lorenzon, X. -G. Lu, X. -R. Lu, B. -Q. Ma, D. Mahon, N. C. R. Makins, S. I. Manaenkov, L. Manfre, Y. Mao, B. Marianski, A. Martinez de la Ossa, H. Marukyan, C. A. Miller, A. Movsisyan, V. Muccifora, M. Murray, D. Mueller, A. Mussgiller, E. Nappi, Y. Naryshkin, A. Nass, M. Negodaev, W. -D. Nowak, L. L. Pappalardo, R. Perez-Benito, N. Pickert, M. Raithel, P. E. Reimer, A. R. Reolon, C. Riedl, K. Rith, G. Rosner, A. Rostomyan, J. Rubin, D. Ryckbosch, Y. Salomatin, F. Sanftl, A. Schaefer, G. Schnell, K. P. Schueler, B. Seitz, T. -A. Shibata, V. Shutov, M. Stancari, M. Statera, E. Steffens, J. J. M. Steijger, H. Stenzel, J. Stewart, F. Stinzing, S. Taroian, A. Terkulov, A. Trzcinski, M. Tytgat, A. Vandenbroucke, P. B. Van der Nat, Y. Van Haarlem, C. Van Hulse, D. Veretennikov, V. Vikhrov, I. Vilardi, C. Vogel, S. Wang, S. Yaschenko, Z. Ye, S. Yen, W. Yu, D. Zeiler, B. Zihlmann, P. Zupranski

Azimuthal asymmetries in exclusive electroproduction of a real photon from a longitudinally polarized deuterium target are measured with respect to target polarization alone and with respect to target polarization combined with beam helicity and/or beam charge. The asymmetries appear in the distribution of the real photons in the azimuthal angle $\phi$ around the virtual photon direction, relative to the lepton scattering plane. The asymmetries arise from the deeply virtual Compton scattering process and its interference with the Bethe-Heitler process. Read More

2010Jun
Authors: HERMES collaboration, A. Airapetian, N. Akopov, Z. Akopov, E. C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetisyan, A. Bacchetta, S. Belostotski, N. Bianchi, H. P. Blok, A. Borissov, J. Bowles, I. Brodski, V. Bryzgalov, J. Burns, M. Capiluppi, G. P. Capitani, E. Cisbani, G. Ciullo, M. Contalbrigo, P. F. Dalpiaz, W. Deconinck, R. De Leo, L. De Nardo, E. De Sanctis, M. Diefenthaler, P. Di Nezza, M. Dueren, M. Ehrenfried, G. Elbakian, F. Ellinghaus, U. Elschenbroich, R. Fabbri, A. Fantoni, L. Felawka, S. Frullani, D. Gabbert, G. Gapienko, V. Gapienko, F. Garibaldi, V. Gharibyan, F. Giordano, S. Gliske, M. Golembiovskaya, C. Hadjidakis, M. Hartig, D. Hasch, G. Hill, A. Hillenbrand, M. Hoek, Y. Holler, I. Hristova, Y. Imazu, A. Ivanilov, A. Izotov, H. E. Jackson, H. S. Jo, S. Joosten, R. Kaiser, G. Karyan, T. Keri, E. Kinney, A. Kisselev, N. Kobayashi, V. Korotkov, V. Kozlov, P. Kravchenko, L. Lagamba, R. Lamb, L. Lapikas, I. Lehmann, P. Lenisa, L. A. Linden-Levy, A. Lopez Ruiz, W. Lorenzon, X. -G. Lu, X. -R. Lu, B. -Q. Ma, D. Mahon, N. C. R. Makins, S. I. Manaenkov, L. Manfre, Y. Mao, B. Marianski, A. Martinez de la Ossa, H. Marukyan, C. A. Miller, Y. Miyachi, A. Movsisyan, M. Murray, A. Mussgiller, E. Nappi, Y. Naryshkin, A. Nass, M. Negodaev, W. -D. Nowak, L. L. Pappalardo, R. Perez-Benito, N. Pickert, M. Raithel, P. E. Reimer, A. R. Reolon, C. Riedl, K. Rith, G. Rosner, A. Rostomyan, J. Rubin, D. Ryckbosch, Y. Salomatin, F. Sanftl, A. Schaefer, G. Schnell, B. Seitz, T. -A. Shibata, V. Shutov, M. Stancari, M. Statera, E. Steffens, J. J. M. Steijger, H. Stenzel, J. Stewart, F. Stinzing, S. Taroian, A. Terkulov, A. Trzcinski, M. Tytgat, P. B. van der Nat, Y. Van Haarlem, C. Van Hulse, D. Veretennikov, V. Vikhrov, I. Vilardi, C. Vogel, S. Wang, S. Yaschenko, H. Ye, Z. Ye, S. Yen, W. Yu, D. Zeiler, B. Zihlmann, P. Zupranski

Single-spin asymmetries for pions and charged kaons are measured in semi-inclusive deep-inelastic scattering of positrons and electrons off a transversely nuclear-polarized hydrogen target. The dependence of the cross section on the azimuthal angles of the target polarization (phi_S)and the produced hadron (phi) is found to have a substantial sin(phi+phi_S) modulation for the production of pi+, pi- and K+. This Fourier component can be interpreted in terms of non-zero transversity distribution functions and non-zero favored and disfavored Collins fragmentation functions with opposite sign. Read More

2010Apr
Authors: The HERMES Collaboration, A. Airapetian, N. Akopov, Z. Akopov, E. C. Aschenauer, W. Augustyniak, R. Avakian, A. Avetissian, E. Avetisyan, B. Ball, S. Belostotski, N. Bianchi, H. P. Blok, H. Boettcher, A. Borissov, J. Bowles, I. Brodski, V. Bryzgalov, J. Burns, M. Capiluppi, G. P. Capitani, E. Cisbani, G. Ciullo, M. Contalbrigo, P. F. Dalpiaz, W. Deconinck, R. De Leo, L. De Nardo, E. De Sanctis, M. Diefenthaler, P. Di Nezza, M. Dueren, M. Ehrenfried, G. Elbakian, F. Ellinghaus, R. Fabbri, A. Fantoni, L. Felawka, S. Frullani, D. Gabbert, G. Gapienko, V. Gapienko, F. Garibaldi, G. Gavrilov, V. Gharibyan, F. Giordano, S. Gliske, M. Golembiovskaya, C. Hadjidakis, M. Hartig, D. Hasch, G. Hill, A. Hillenbrand, M. Hoek, Y. Holler, I. Hristova, Y. Imazu, A. Ivanilov, A. Izotov, H. E. Jackson, H. S. Jo, S. Joosten, R. Kaiser, G. Karyan, T. Keri, E. Kinney, A. Kisselev, N. Kobayashi, V. Korotkov, V. Kozlov, P. Kravchenko, V. G. Krivokhijne, L. Lagamba, R. Lamb, L. Lapikas, I. Lehmann, P. Lenisa, L. A. Linden-Levy, A. Lopez~Ruiz, W. Lorenzon, X. -G. Lu, X. -R. Lu, B. -Q. Ma, D. Mahon, N. C. R. Makins, S. I. Manaenkov, L. Manfre, Y. Mao, B. Marianski, A. Martinez de la Ossa, H. Marukyan, C. A. Miller, Y. Miyachi, A. Movsisyan, V. Muccifora, M. Murray, A. Mussgiller, E. Nappi, Y. Naryshkin, A. Nass, M. Negodaev, W. -D. Nowak, L. L. Pappalardo, R. Perez-Benito, N. Pickert, M. Raithel, P. E. Reimer, A. R. Reolon, C. Riedl, K. Rith, G. Rosner, A. Rostomyan, J. Rubin, D. Ryckbosch, Y. Salomatin, F. Sanftl, A. Schaefer, G. Schnell, K. P. Schueler, B. Seitz, T. -A. Shibata, V. Shutov, M. Stancari, M. Statera, E. Steffens, J. J. M. Steijger, H. Stenzel, J. Stewart, F. Stinzing, S. Taroian, A. Terkulov, A. Trzcinski, M. Tytgat, A. Vandenbroucke, P. B. van der Nat, Y. Van Haarlem, C. Van Hulse, D. Veretennikov, V. Vikhrov, I. Vilardi, C. Vogel, S. Wang, S. Yaschenko, H. Ye, Z. Ye, S. Yen, W. Yu, D. Zeiler, B. Zihlmann, P. Zupranski

Polarisation asymmetries are measured for the hard exclusive leptoproduction of real photons from a longitudinally polarised hydrogen target. These asymmetries arise from the deeply virtual Compton scattering and Bethe-Heitler processes. From the data are extracted two asymmetries in the azimuthal distribution of produced real photons about the direction of the exchanged virtual photon: A_UL with respect to the target polarisation and A_LL with respect to the product of the beam and target polarisations. Read More

The improved two-scale model is used to perform the fit to the semi-inclusive deep-inelastic scattering (SIDIS) data of HERMES experiment at DESY on nuclear targets. The ratio of hadron multiplicity on nuclear target to the deuterium one is chosen as observable, as usually. The two-parameter's fit gives satisfactory agreement with the data in term of $\chi^2$ criterium. Read More

2009Apr

We propose to use an internal polarized hydrogen storage cell gas target in the AD ring to determine for the first time the two total spin-dependent pbar-p cross sections sigma_1 and sigma_2 at antiproton beam energies in the range from 50 to 450 MeV. The data obtained are of interest by themselves for the general theory of pbar-p interactions since they will provide a first experimental constraint of the spin-spin dependence of the nucleon-antinucleon potential in the energy range of interest. In addition, measurements of the polarization buildup of stored antiprotons are required to define the optimum parameters of a future, dedicated Antiproton Polarizer Ring (APR), intended to feed a double-polarized asymmetric pbar-p collider with polarized antiprotons. Read More

In this paper it is demonstrated that based on two-dimensional distributions in semi-inclusive deep inelastic scattering (SIDIS) data, obtained recently by the HERMES experiment at DESY on different nuclei, which contains data for charged pions produced in $z$ slices as a function of $\nu$, and in a $\nu$ slices as a function of $z$, it it is possible to parametrise a ratio of multiplicities on nucleus and deuterium (per nucleon) $R_M^{h}$ in a form of a function of a single variable $\tau$, which has the physical meaning of the formation time of hadron. We call this effect $\tau$ scaling. $\tau$ is a function of two variables $\nu$ and $z$. Read More

This article presents the $A$-dependence of the differential cross section for the coherent electroproduction of vector mesons on nuclei in forward direction, at fixed values of longitudinal momentum transfer $q_{L}$. It is shown that such cross section has complicated behavior over the atomic mass number $A$ with local minimums and maximums. It is also shown that a ratio of the real to the imaginary parts of the forward coherent amplitude on nuclei $\alpha_{A} = \Re e{f_{A}} / \Im m{f_{A}}$ has breaking points at some values of $A$. Read More

One of the basic assumptions of the string model is that as a result of a DIS in nucleus a single string arises, which then breaks into hadrons. However the pomeron exchange considered in this work, leads to the production of two strings in the one event. The hadrons produced in these events have smaller formation lengths, than those with the same energy produced in the single string events. Read More

Based on the nuclear attenuation data obtained by the HERMES experiment on nitrogen and krypton nuclei, it is shown that the nuclear attenuation $R_M^{h}$ can be parametrised in a form of a linear polynomial $P_1=a_{11}$ + $\tau a_{12}$, where $\tau$ is the formation time, which depends on the energy of the virtual photon $\nu$ and fraction of that energy $z$ carried by the final hadron. Three widely known parameterizations for $\tau$ were used for the performed fit. The fit parameters $a_{11}$ and $a_{12}$ do not depend on $\nu$ and $z$. Read More

Nuclear attenuation of the two-hadron system is considered in the string model. The two-scale model and its improved version with two different choices of constituent formation time and sets of parameters obtained earlier for the single hadron attenuation, are used to describe available experimental data for the $z$-dependence of subleading hadron, whereas satisfactory agreement with the experimental data has been observed. A model prediction for $\nu$-dependence of the nuclear attenuation of the two-hadron system is also presented. Read More

The Two-Scale Model and its improved version were used to perform the fit to the HERMES data for $\nu$ (the virtual photon energy) and z (the fraction of $\nu$ carried by hadron) dependencies of nuclear multiplicity ratios for $\pi^+$ and $\pi^-$ mesons electro-produced on two nuclear targets ($^{14}$N and $^{84}$Kr). The quantitative criterium $\chi ^2$ was used for the first time to analyse the results of the model fit to the nuclear multiplicity ratios data. The two-parameter's fit gives satisfactory agreement with the HERMES data. Read More

This paper describes the use of the time-of-flight (TOF) technique as a particle identification method for the HERMES experiment. The time-of-flight is measured by two 1x4 m^2 scintillation hodoscopes that initially were designed for the first-level trigger only. However, the suitable time structure of the HERA electron beam allows an extension of their functions to also measure the TOF for low momentum hadron identification. Read More

We propose extended version of stationary string model to describe the nuclear attenuation. This model takes into account flavour content of particles and allows to include into consideration all hadrons created from string. The predictions of the model are compared with experimental results obtained by HERMES collaboration (DESY) on different nuclei (N and Kr). Read More

The construction and use of a dual radiator Ring Imaging Cerenkov(RICH) detector is described. This instrument was developed for the HERMES experiment at DESY which emphasizes measurements of semi-inclusive deep-inelastic scattering. It provides particle identification for pions, kaons, and protons in the momentum range from 2 to 15 GeV, which is essential to these studies. Read More

An asynchronous accelerator is described, in which the principle of its operation permits the active longitudinal bunch compression of accelerated proton beams, to overcome the space charge limitation effects of intense bunches. It is shown that accelerated bunches from an RFQ linac can be adapted for Asynchronac injection for a multiple of choices in the acceleration frequencies of the RFQ and the Asynchronac. The offered new type of accelerator system is especially suitable to accelerate proton beams for up to 100MeV energy and hundreds of mA average current. Read More

The possibility to convert the photon beam linear polarization into circular one at photon energies of hundreds GeV with the use of crystals is considered. The energy and orientation dependencies of refractive indexes are investigated in case of diamond, silicon and germanium crystal targets. To maximize the values for figure of merit, the corresponding crystal optimal orientation angles and thickness are found. Read More

The concept of large-radius multistage coaxial cyclotrons having separated orbits is described, to generate proton beams of 120-2000 MeV energy at tens of GW pulsed and hundreds of MW in continuous beam power operation. Accelerated beam losses must be less than 0.1 W/m for the intercepted average beam power linear density. Read More

We analyze the structure of the periodic trajectories of the matrix generator of pseudorandom numbers which has been proposed earlier. The structure of the periodic trajectories becomes more transparent when the rational sublattice coincides with the Galois field $GF[p]$. We are able to compute the period of the trajectories as a function of $p$ and the dimension of the matrix $d$. Read More

We suggest fast algorithm for the matrix generator of pseudorandom numbers based on Kolmogorov-Anosov K systems which has been earliar proposed in \cite{savvidy1,akopov1}. This algorithm reduces $N^{2}$ operation of the matrix generator to $NlnN$ and essentially reduces the generation time. It also clarifies the algebraic structure of this type of K system generators. Read More