A. Mkrtchyan - HKS - JLab E05-115 and E01-001 - Collaborations

A. Mkrtchyan
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A. Mkrtchyan
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HKS - JLab E05-115 and E01-001 - Collaborations
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Nuclear Experiment (21)
 
Physics - Accelerator Physics (9)
 
Physics - Instrumentation and Detectors (8)
 
High Energy Physics - Theory (7)
 
Nuclear Theory (4)
 
Physics - Other (4)
 
Physics - Classical Physics (3)
 
Mathematics - Group Theory (2)
 
High Energy Physics - Experiment (2)
 
Mathematics - Logic (1)
 
Mathematics - Rings and Algebras (1)
 
Physics - Soft Condensed Matter (1)
 
High Energy Physics - Phenomenology (1)
 
Mathematics - Metric Geometry (1)
 
Quantum Physics (1)
 
General Relativity and Quantum Cosmology (1)
 
Quantitative Biology - Quantitative Methods (1)
 
Quantitative Biology - Cell Behavior (1)
 
Mathematics - Functional Analysis (1)
 
Mathematics - Differential Geometry (1)
 
Physics - Optics (1)

Publications Authored By A. Mkrtchyan

This workshop aimed at producing an optimized photon source concept with potential increase of scientific output at Jefferson Lab, and at refining the science for hadron physics experiments benefitting from such a high-intensity photon source. The workshop brought together the communities directly using such sources for photo-production experiments, or for conversion into $K_L$ beams. The combination of high precision calorimetry and high intensity photon sources greatly enhances scientific benefit to (deep) exclusive processes like wide-angle and time-like Compton scattering. Read More

We have performed a novel comparison between electron-beam polarimeters based on M{\o}ller and Compton scattering. A sequence of electron-beam polarization measurements were performed at low beam currents ($<$ 5 $\mu$A) during the $Q_{\rm weak}$ experiment in Hall C at Jefferson Lab. These low current measurements were bracketed by the regular high current (180 $\mu$A) operation of the Compton polarimeter. Read More

We investigate combined effects of nontrivial topology, induced by a cosmic string, and boundaries on the fermionic condensate and the vacuum expectation value (VEV) of the energy-momentum tensor for a massive fermionic field. As geometry of boundaries we consider two plates perpendicular to the string axis on which the field is constrained by the MIT bag boundary condition. By using the Abel-Plana type summation formula, the VEVs in the region between the plates are decomposed into the boundary-free and boundary-induced contributions for general case of the planar angle deficit. Read More

Hadronic reactions producing strange quarks such as exclusive or semi-inclusive kaon production, play an important role in studies of hadron structure and the dynamics that bind the most basic elements of nuclear physics. The small-angle capability of the new Super High Momentum Spectrometer (SHMS) in Hall C, coupled with its high momentum reach - up to the anticipated 11-GeV beam energy in Hall C - and coincidence capability with the well-understood High Momentum Spectrometer, will allow for probes of such hadron structure involving strangeness down to the smallest distance scales to date. To cleanly select the kaons, a threshold aerogel Cerenkov detector has been constructed for the SHMS. Read More

We investigate the radiation from a charge rotating around conductors with cylindrical symmetry. First the problem is considered with a charge rotating around a conducting cylinder immersed in a homogeneous medium. The surface charge and current densities induced on the cylinder surface are evaluated. Read More

2016Jun
Affiliations: 1HKS, 2HKS, 3HKS, 4HKS, 5HKS, 6HKS, 7HKS, 8HKS, 9HKS, 10HKS, 11HKS, 12HKS, 13HKS, 14HKS, 15HKS, 16HKS, 17HKS, 18HKS, 19HKS, 20HKS, 21HKS, 22HKS, 23HKS, 24HKS, 25HKS, 26HKS, 27HKS, 28HKS, 29HKS, 30HKS, 31HKS, 32HKS, 33HKS, 34HKS, 35HKS, 36HKS, 37HKS, 38HKS, 39HKS, 40HKS, 41HKS, 42HKS, 43HKS, 44HKS, 45HKS, 46HKS, 47HKS, 48HKS, 49HKS, 50HKS, 51HKS, 52HKS, 53HKS, 54HKS, 55HKS, 56HKS, 57HKS, 58HKS, 59HKS, 60HKS, 61HKS, 62HKS, 63HKS, 64HKS, 65HKS, 66HKS, 67HKS, 68HKS, 69HKS, 70HKS, 71HKS, 72HKS, 73HKS, 74HKS, 75HKS, 76HKS, 77HKS, 78HKS, 79HKS, 80HKS, 81HKS, 82HKS, 83HKS, 84HKS, 85HKS, 86HKS

The missing mass spectroscopy of the $^{7}_{\Lambda}$He hypernucleus was performed, using the $^{7}$Li$(e,e^{\prime}K^{+})^{7}_{\Lambda}$He reaction at the Thomas Jefferson National Accelerator Facility Hall C. The $\Lambda$ binding energy of the ground state (1/2$^{+}$) was determined with a smaller error than that of the previous measurement, being $B_{\Lambda}$ = 5.55 $\pm$ 0. Read More

Regression of Hensen's node from anterior to posterior is driving the elongation and patterning of avian embryo body. Recent experiments link gradient of presomitic mesoderm cell motility to displacement of the node and body axis elongation. Ingression of new cells into presomitic mesoderm tissue also contributes to the process. Read More

We intrinsically study the conformal transformations on metric measure spaces, including the Sobolev space, the differential structure and the curvature-dimension condition under conformal transformations. As an application, we will show how the conformal transformations change the curvature-dimension condition. Read More

We investigate the transition radiation on a periodically deformed interface between two dielectric media. Under the assumption that the dielectric permittivities of the media are close, a formula is derived for the spectral-angular distribution of the radiated energy in the general case of non-static profile function for the separating boundary. In particular, the latter includes the case of surface waves propagating along the boundary. Read More

We report on the highest precision yet achieved in the measurement of the polarization of a low energy, $\mathcal{O}$(1 GeV), electron beam, accomplished using a new polarimeter based on electron-photon scattering, in Hall~C at Jefferson Lab. A number of technical innovations were necessary, including a novel method for precise control of the laser polarization in a cavity and a novel diamond micro-strip detector which was able to capture most of the spectrum of scattered electrons. The data analysis technique exploited track finding, the high granularity of the detector and its large acceptance. Read More

We prove a general divisibility theorem that implies, e.g., that, in any group, the number of generating pairs (as well as triples, etc. Read More

For the production of a polarized antiproton beam various methods have been suggested including the possibility that antiprotons may be produced polarized which will be checked experimentally. The polarization of antiprotons produced under typical conditions for antiproton beam preparation will be measured at the CERN/PS. If the production process creates some polarization a polarized antiproton beam could be prepared by a rather simple modification of the antiproton beam facility. Read More

2014Sep
Authors: Qweak Collaboration, T. Allison, M. Anderson, D. Androic, D. S. Armstrong, A. Asaturyan, T. D. Averett, R. Averill, J. Balewski, J. Beaufait, R. S. Beminiwattha, J. Benesch, F. Benmokhtar, J. Bessuille, J. Birchall, E. Bonnell, J. Bowman, P. Brindza, D. B. Brown, R. D. Carlini, G. D. Cates, B. Cavness, G. Clark, J. C. Cornejo, S. Covrig Dusa, M. M. Dalton, C. A. Davis, D. C. Dean, W. Deconinck, J. Diefenbach, K. Dow, J. F. Dowd, J. A. Dunne, D. Dutta, W. S. Duvall, J. R. Echols, M. Elaasar, W. R. Falk, K. D. Finelli, J. M. Finn, D. Gaskell, M. T. W. Gericke, J. Grames, V. M. Gray, K. Grimm, F. Guo, J. Hansknecht, D. J. Harrison, E. Henderson, J. R. Hoskins, E. Ihloff, K. Johnston, D. Jones, M. Jones, R. Jones, M. Kargiantoulakis, J. Kelsey, N. Khan, P. M. King, E. Korkmaz, S. Kowalski, A. Kubera, J. Leacock, J. P. Leckey, A. R. Lee, J. H. Lee, L. Lee, Y. Liang, S. MacEwan, D. Mack, J. A. Magee, R. Mahurin, J. Mammei, J. W. Martin, A. McCreary, M. H. McDonald, M. J. McHugh, P. Medeiros, D. Meekins, J. Mei, R. Michaels, A. Micherdzinska, A. Mkrtchyan, H. Mkrtchyan, N. Morgan, J. Musson, K. E. Mesick, A. Narayan, L. Z. Ndukum, V. Nelyubin, Nuruzzaman, W. T. H. van Oers, A. K. Opper, S. A. Page, J. Pan, K. D. Paschke, S. K. Phillips, M. L. Pitt, M. Poelker, J. F. Rajotte, W. D. Ramsay, W. R. Roberts, J. Roche, P. W. Rose, B. Sawatzky, T. Seva, M. H. Shabestari, R. Silwal, N. Simicevic, G. R. Smith, S. Sobczynski, P. Solvignon, D. T. Spayde, B. Stokes, D. W. Storey, A. Subedi, R. Subedi, R. Suleiman, V. Tadevosyan, W. A. Tobias, V. Tvaskis, E. Urban, B. Waidyawansa, P. Wang, S. P. Wells, S. A. Wood, S. Yang, S. Zhamkochyan, R. B. Zielinski

The Jefferson Lab Q_weak experiment determined the weak charge of the proton by measuring the parity-violating elastic scattering asymmetry of longitudinally polarized electrons from an unpolarized liquid hydrogen target at small momentum transfer. A custom apparatus was designed for this experiment to meet the technical challenges presented by the smallest and most precise ${\vec{e}}$p asymmetry ever measured. Technical milestones were achieved at Jefferson Lab in target power, beam current, beam helicity reversal rate, polarimetry, detected rates, and control of helicity-correlated beam properties. Read More

2014Jun
Authors: L. Tang1, C. Chen2, T. Gogami3, D. Kawama4, Y. Han5, L. Yuan6, A. Matsumura7, Y. Okayasu8, T. Seva9, V. M. Rodriguez10, P. Baturin11, A. Acha12, P. Achenbach13, A. Ahmidouch14, I. Albayrak15, D. Androic16, A. Asaturyan17, R. Asaturyan18, O. Ates19, R. Badui20, O. K. Baker21, F. Benmokhtar22, W. Boeglin23, J. Bono24, P. Bosted25, E. Brash26, P. Carter27, R. Carlini28, A. Chiba29, M. E. Christy30, L. Cole31, M. M. Dalton32, S. Danagoulian33, A. Daniel34, R. De Leo35, V. Dharmawardane36, D. Doi37, K. Egiyan38, M. Elaasar39, R. Ent40, H. Fenker41, Y. Fujii42, M. Furic43, M. Gabrielyan44, L. Gan45, F. Garibaldi46, D. Gaskell47, A. Gasparian48, E. F. Gibson49, P. Gueye50, O. Hashimoto51, D. Honda52, T. Horn53, B. Hu54, Ed V. Hungerford55, C. Jayalath56, M. Jones57, K. Johnston58, N. Kalantarians59, H. Kanda60, M. Kaneta61, F. Kato62, S. Kato63, M. Kawai64, C. Keppel65, H. Khanal66, M. Kohl67, L. Kramer68, K. J. Lan69, Y. Li70, A. Liyanage71, W. Luo72, D. Mack73, K. Maeda74, S. Malace75, A. Margaryan76, G. Marikyan77, P. Markowitz78, T. Maruta79, N. Maruyama80, V. Maxwell81, D. J. Millener82, T. Miyoshi83, A. Mkrtchyan84, H. Mkrtchyan85, T. Motoba86, S. Nagao87, S. N. Nakamura88, A. Narayan89, C. Neville90, G. Niculescu91, M. I. Niculescu92, A. Nunez93, Nuruzzaman94, H. Nomura95, K. Nonaka96, A. Ohtani97, M. Oyamada98, N. Perez99, T. Petkovic100, J. Pochodzalla101, X. Qiu102, S. Randeniya103, B. Raue104, J. Reinhold105, R. Rivera106, J. Roche107, C. Samanta108, Y. Sato109, B. Sawatzky110, E. K. Segbefia111, D. Schott112, A. Shichijo113, N. Simicevic114, G. Smith115, Y. Song116, M. Sumihama117, V. Tadevosyan118, T. Takahashi119, N. Taniya120, K. Tsukada121, V. Tvaskis122, M. Veilleux123, W. Vulcan124, S. Wells125, F. R. Wesselmann126, S. A. Wood127, T. Yamamoto128, C. Yan129, Z. Ye130, K. Yokota131, S. Zhamkochyan132, L. Zhu133
Affiliations: 1HKS - JLab E05-115 and E01-001 - Collaborations, 2HKS - JLab E05-115 and E01-001 - Collaborations, 3HKS - JLab E05-115 and E01-001 - Collaborations, 4HKS - JLab E05-115 and E01-001 - Collaborations, 5HKS - JLab E05-115 and E01-001 - Collaborations, 6HKS - JLab E05-115 and E01-001 - Collaborations, 7HKS - JLab E05-115 and E01-001 - Collaborations, 8HKS - JLab E05-115 and E01-001 - Collaborations, 9HKS - JLab E05-115 and E01-001 - Collaborations, 10HKS - JLab E05-115 and E01-001 - Collaborations, 11HKS - JLab E05-115 and E01-001 - Collaborations, 12HKS - JLab E05-115 and E01-001 - Collaborations, 13HKS - JLab E05-115 and E01-001 - Collaborations, 14HKS - JLab E05-115 and E01-001 - Collaborations, 15HKS - JLab E05-115 and E01-001 - Collaborations, 16HKS - JLab E05-115 and E01-001 - Collaborations, 17HKS - JLab E05-115 and E01-001 - Collaborations, 18HKS - JLab E05-115 and E01-001 - Collaborations, 19HKS - JLab E05-115 and E01-001 - Collaborations, 20HKS - JLab E05-115 and E01-001 - Collaborations, 21HKS - JLab E05-115 and E01-001 - Collaborations, 22HKS - JLab E05-115 and E01-001 - Collaborations, 23HKS - JLab E05-115 and E01-001 - Collaborations, 24HKS - JLab E05-115 and E01-001 - Collaborations, 25HKS - JLab E05-115 and E01-001 - Collaborations, 26HKS - JLab E05-115 and E01-001 - Collaborations, 27HKS - JLab E05-115 and E01-001 - Collaborations, 28HKS - JLab E05-115 and E01-001 - Collaborations, 29HKS - JLab E05-115 and E01-001 - Collaborations, 30HKS - JLab E05-115 and E01-001 - Collaborations, 31HKS - JLab E05-115 and E01-001 - Collaborations, 32HKS - JLab E05-115 and E01-001 - Collaborations, 33HKS - JLab E05-115 and E01-001 - Collaborations, 34HKS - JLab E05-115 and E01-001 - Collaborations, 35HKS - JLab E05-115 and E01-001 - Collaborations, 36HKS - JLab E05-115 and E01-001 - Collaborations, 37HKS - JLab E05-115 and E01-001 - Collaborations, 38HKS - JLab E05-115 and E01-001 - Collaborations, 39HKS - JLab E05-115 and E01-001 - Collaborations, 40HKS - JLab E05-115 and E01-001 - Collaborations, 41HKS - JLab E05-115 and E01-001 - Collaborations, 42HKS - JLab E05-115 and E01-001 - Collaborations, 43HKS - JLab E05-115 and E01-001 - Collaborations, 44HKS - JLab E05-115 and E01-001 - Collaborations, 45HKS - JLab E05-115 and E01-001 - Collaborations, 46HKS - JLab E05-115 and E01-001 - Collaborations, 47HKS - JLab E05-115 and E01-001 - Collaborations, 48HKS - JLab E05-115 and E01-001 - Collaborations, 49HKS - JLab E05-115 and E01-001 - Collaborations, 50HKS - JLab E05-115 and E01-001 - Collaborations, 51HKS - JLab E05-115 and E01-001 - Collaborations, 52HKS - JLab E05-115 and E01-001 - Collaborations, 53HKS - JLab E05-115 and E01-001 - Collaborations, 54HKS - JLab E05-115 and E01-001 - Collaborations, 55HKS - JLab E05-115 and E01-001 - Collaborations, 56HKS - JLab E05-115 and E01-001 - Collaborations, 57HKS - JLab E05-115 and E01-001 - Collaborations, 58HKS - JLab E05-115 and E01-001 - Collaborations, 59HKS - JLab E05-115 and E01-001 - Collaborations, 60HKS - JLab E05-115 and E01-001 - Collaborations, 61HKS - JLab E05-115 and E01-001 - Collaborations, 62HKS - JLab E05-115 and E01-001 - Collaborations, 63HKS - JLab E05-115 and E01-001 - Collaborations, 64HKS - JLab E05-115 and E01-001 - Collaborations, 65HKS - JLab E05-115 and E01-001 - Collaborations, 66HKS - JLab E05-115 and E01-001 - Collaborations, 67HKS - JLab E05-115 and E01-001 - Collaborations, 68HKS - JLab E05-115 and E01-001 - Collaborations, 69HKS - JLab E05-115 and E01-001 - Collaborations, 70HKS - JLab E05-115 and E01-001 - Collaborations, 71HKS - JLab E05-115 and E01-001 - Collaborations, 72HKS - JLab E05-115 and E01-001 - Collaborations, 73HKS - JLab E05-115 and E01-001 - Collaborations, 74HKS - JLab E05-115 and E01-001 - Collaborations, 75HKS - JLab E05-115 and E01-001 - Collaborations, 76HKS - JLab E05-115 and E01-001 - Collaborations, 77HKS - JLab E05-115 and E01-001 - Collaborations, 78HKS - JLab E05-115 and E01-001 - Collaborations, 79HKS - JLab E05-115 and E01-001 - Collaborations, 80HKS - JLab E05-115 and E01-001 - Collaborations, 81HKS - JLab E05-115 and E01-001 - Collaborations, 82HKS - JLab E05-115 and E01-001 - Collaborations, 83HKS - JLab E05-115 and E01-001 - Collaborations, 84HKS - JLab E05-115 and E01-001 - Collaborations, 85HKS - JLab E05-115 and E01-001 - Collaborations, 86HKS - JLab E05-115 and E01-001 - Collaborations, 87HKS - JLab E05-115 and E01-001 - Collaborations, 88HKS - JLab E05-115 and E01-001 - Collaborations, 89HKS - JLab E05-115 and E01-001 - Collaborations, 90HKS - JLab E05-115 and E01-001 - Collaborations, 91HKS - JLab E05-115 and E01-001 - Collaborations, 92HKS - JLab E05-115 and E01-001 - Collaborations, 93HKS - JLab E05-115 and E01-001 - Collaborations, 94HKS - JLab E05-115 and E01-001 - Collaborations, 95HKS - JLab E05-115 and E01-001 - Collaborations, 96HKS - JLab E05-115 and E01-001 - Collaborations, 97HKS - JLab E05-115 and E01-001 - Collaborations, 98HKS - JLab E05-115 and E01-001 - Collaborations, 99HKS - JLab E05-115 and E01-001 - Collaborations, 100HKS - JLab E05-115 and E01-001 - Collaborations, 101HKS - JLab E05-115 and E01-001 - Collaborations, 102HKS - JLab E05-115 and E01-001 - Collaborations, 103HKS - JLab E05-115 and E01-001 - Collaborations, 104HKS - JLab E05-115 and E01-001 - Collaborations, 105HKS - JLab E05-115 and E01-001 - Collaborations, 106HKS - JLab E05-115 and E01-001 - Collaborations, 107HKS - JLab E05-115 and E01-001 - Collaborations, 108HKS - JLab E05-115 and E01-001 - Collaborations, 109HKS - JLab E05-115 and E01-001 - Collaborations, 110HKS - JLab E05-115 and E01-001 - Collaborations, 111HKS - JLab E05-115 and E01-001 - Collaborations, 112HKS - JLab E05-115 and E01-001 - Collaborations, 113HKS - JLab E05-115 and E01-001 - Collaborations, 114HKS - JLab E05-115 and E01-001 - Collaborations, 115HKS - JLab E05-115 and E01-001 - Collaborations, 116HKS - JLab E05-115 and E01-001 - Collaborations, 117HKS - JLab E05-115 and E01-001 - Collaborations, 118HKS - JLab E05-115 and E01-001 - Collaborations, 119HKS - JLab E05-115 and E01-001 - Collaborations, 120HKS - JLab E05-115 and E01-001 - Collaborations, 121HKS - JLab E05-115 and E01-001 - Collaborations, 122HKS - JLab E05-115 and E01-001 - Collaborations, 123HKS - JLab E05-115 and E01-001 - Collaborations, 124HKS - JLab E05-115 and E01-001 - Collaborations, 125HKS - JLab E05-115 and E01-001 - Collaborations, 126HKS - JLab E05-115 and E01-001 - Collaborations, 127HKS - JLab E05-115 and E01-001 - Collaborations, 128HKS - JLab E05-115 and E01-001 - Collaborations, 129HKS - JLab E05-115 and E01-001 - Collaborations, 130HKS - JLab E05-115 and E01-001 - Collaborations, 131HKS - JLab E05-115 and E01-001 - Collaborations, 132HKS - JLab E05-115 and E01-001 - Collaborations, 133HKS - JLab E05-115 and E01-001 - Collaborations

Since the pioneering experiment, E89-009 studying hypernuclear spectroscopy using the $(e,e^{\prime}K^+)$ reaction was completed, two additional experiments, E01-011 and E05-115, were performed at Jefferson Lab. These later experiments used a modified experimental design, the "tilt method", to dramatically suppress the large electromagnetic background, and allowed for a substantial increase in luminosity. Additionally, a new kaon spectrometer, HKS (E01-011), a new electron spectrometer, HES, and a new splitting magnet were added to produce precision, high-resolution hypernuclear spectroscopy. Read More

A subset of results from the recently completed Jefferson Lab Qweak experiment are reported. This experiment, sensitive to physics beyond the Standard Model, exploits the small parity-violating asymmetry in elastic ep scattering to provide the first determination of the protons weak charge Qweak(p). The experiment employed a 180 uA longitudinally polarized 1. Read More

The Qweak experiment has measured the parity-violating asymmetry in polarized e-p elastic scattering at Q^2 = 0.025(GeV/c)^2, employing 145 microamps of 89% longitudinally polarized electrons on a 34.4cm long liquid hydrogen target at Jefferson Lab. Read More

Aerogel and water Cerenkov detectors were employed to tag kaons for a lambda hypernuclear spectroscopic experiment which used the (e,e'K+) reaction in experimental Hall C at Jefferson Lab (JLab E05-115). Fringe fields from the kaon spectrometer magnet yielded ~5 Gauss at the photomultiplier tubes (PMT) for these detectors which could not be easily shielded. As this field results in a lowered kaon detection efficiency, we implemented a bucking coil on each photomultiplier tubes to actively cancel this magnetic field, thus maximizing kaon detection efficiency. Read More

The lifetime of a Lambda particle embedded in a nucleus (hypernucleus) decreases from that of free Lambda decay due to the opening of the Lambda N to NN weak decay channel. However, it is generally believed that the lifetime of a hypernucleus attains a constant value (saturation) for medium to heavy hypernuclear masses, yet this hypothesis has been difficult to verify. The present paper reports a direct measurement of the lifetime of medium-heavy hypernuclei produced with a photon-beam from Fe, Cu, Ag, and Bi targets. Read More

2012Jul
Affiliations: 1HKS, 2HKS, 3HKS, 4HKS, 5HKS, 6HKS, 7HKS, 8HKS, 9HKS, 10HKS, 11HKS, 12HKS, 13HKS, 14HKS, 15HKS, 16HKS, 17HKS, 18HKS, 19HKS, 20HKS, 21HKS, 22HKS, 23HKS, 24HKS, 25HKS, 26HKS, 27HKS, 28HKS, 29HKS, 30HKS, 31HKS, 32HKS, 33HKS, 34HKS, 35HKS, 36HKS, 37HKS, 38HKS, 39HKS, 40HKS, 41HKS, 42HKS, 43HKS, 44HKS, 45HKS, 46HKS, 47HKS, 48HKS, 49HKS, 50HKS, 51HKS, 52HKS, 53HKS, 54HKS, 55HKS, 56HKS, 57HKS, 58HKS, 59HKS, 60HKS, 61HKS, 62HKS, 63HKS, 64HKS, 65HKS, 66HKS, 67HKS, 68HKS, 69HKS, 70HKS, 71HKS, 72HKS, 73HKS, 74HKS, 75HKS, 76HKS, 77HKS, 78HKS, 79HKS, 80HKS, 81HKS, 82HKS, 83HKS, 84HKS, 85HKS, 86HKS, 87HKS, 88HKS, 89HKS, 90HKS, 91HKS, 92HKS, 93HKS

An experiment with a newly developed high-resolution kaon spectrometer (HKS) and a scattered electron spectrometer with a novel configuration was performed in Hall C at Jefferson Lab (JLab). The ground state of a neutron-rich hypernucleus, He 7 Lambda, was observed for the first time with the (e,e'K+) reaction with an energy resolution of ~0.6 MeV. Read More

Generalising Solomon's theorem, C. Gordon and F. Rodriguez-Villegas have proven recently that, in any group, the number of solutions to a system of coefficient-free equations is divisible by the order of this group whenever the rank of the matrix composed of the exponent sums of i-th unknown in j-th equation is less than the number of unknowns. Read More

The electromagnetic calorimeters of the various magnetic spectrometers in Hall C at Jefferson Lab are presented. For the existing HMS and SOS spectrometers design considerations, relevant construction information, and comparisons of simulated and experimental results are included. The energy resolution of the HMS and SOS calorimeters is better than $\sigma/E \sim 6%/\sqrt E $, and pion/electron ($\pi/e$) separation of about 100:1 has been achieved in energy range 1 -- 5 GeV. Read More

The radiation from a relativistic electron uniformly moving along the axis of cylindrical waveguide filled with laminated material of finite length is investigated. Expressions for the spectral distribution of radiation passing throw the transverse section of waveguide at large distances from the laminated material are derived with no limitations on the amplitude and variation profile of the layered medium permittivity and permeability. Numerical results for layered material consisting of dielectric plates alternated with vacuum gaps are given. Read More

We propose a new precision measurement of parity-violating electron scattering on the proton at very low Q^2 and forward angles to challenge predictions of the Standard Model and search for new physics. A unique opportunity exists to carry out the first precision measurement of the proton's weak charge, $Q_W =1 - 4\sin^2\theta_W$. A 2200 hour measurement of the parity violating asymmetry in elastic ep scattering at Q^2=0. Read More

We present new data for the polarization observables of the final state proton in the $^{1}H(\vec{\gamma},\vec{p})\pi^{0}$ reaction. These data can be used to test predictions based on hadron helicity conservation (HHC) and perturbative QCD (pQCD). These data have both small statistical and systematic uncertainties, and were obtained with beam energies between 1. Read More

Forward transition radiation is considered in an ultrasonic superlattice excited in a finite thickness plate under oblique incidence of relativistic electrons. We investigate the influence of acoustic waves on both the intensity and polarization of the radiation. In the quasi-classical approximation, formulas are derived for the vector potential of the electromagnetic field and for the spectral-angular distribution of the radiation intensity. Read More

A large set of cross sections for semi-inclusive electroproduction of charged pions ($\pi^\pm$) from both proton and deuteron targets was measured. The data are in the deep-inelastic scattering region with invariant mass squared $W^2$ > 4 GeV$^2$ and range in four-momentum transfer squared $2 < Q^2 < 4$ (GeV/c)$^2$, and cover a range in the Bjorken scaling variable 0.2 < x < 0. Read More

2010Dec

Intensive theoretical and experimental efforts over the past decade have aimed at explaining the discrepancy between data for the proton electric to magnetic form factor ratio, $G_{E}/G_{M}$, obtained separately from cross section and polarization transfer measurements. One possible explanation for this difference is a two-photon-exchange (TPEX) contribution. In an effort to search for effects beyond the one-photon-exchange or Born approximation, we report measurements of polarization transfer observables in the elastic $H(\vec{e},e'\vec{p})$ reaction for three different beam energies at a fixed squared momentum transfer $Q^2 = 2. Read More

2010May

Among the most fundamental observables of nucleon structure, electromagnetic form factors are a crucial benchmark for modern calculations describing the strong interaction dynamics of the nucleon's quark constituents; indeed, recent proton data have attracted intense theoretical interest. In this letter, we report new measurements of the proton electromagnetic form factor ratio using the recoil polarization method, at momentum transfers Q2=5.2, 6. Read More

Some part of the microwave Cherenkov radiation from a particle-in-flight from vacuum to semi-infinite layered medium is redirected by the periodical structure of medium in the backward direction. This part of radiation is quasi-monochromatic. Read More

Transition radiation from relativistic electrons is investigated in an ultrasonic superlattice excited in a finite thickness plate. In the quasi-classical approximation formulae are derived for the vector potential of the electromagnetic field and for the spectral-angular distribution of the radiation intensity. The acoustic waves generate new resonance peaks in the spectral and angular distribution of the radiation intensity. Read More

The radiation from a charged particle-in-flight from a semi-infinite laminated medium to vacuum and back,- from vacuum to the laminated medium, has been investigated. Expressions for the spectral-angular distribution of radiation energy in vacuum (at large distances from the boundary of laminated medium) were obtained for both the cases with no limitations on the amplitude and variation profile of the laminated medium permittivity. The results of appropriate numerical calculations are presented and possible applications of the obtained results are discussed. Read More

In the present paper we investigate coherent bremsstrahlung of high energy electrons moving in a periodically deformed single crystal with a complex base. The formula for corresponding differential cross-section is derived for an arbitrary deformation field. The conditions are discussed under which the influence of the deformation is important. Read More

We report on the recent progress in the investigation of the influence of hyperacoustic vibrations on the coherent electron-positron pair creation by high-energy photons in crystals. In dependence of the values for the parameters, the presence of the deformation field can either enhance or reduce the cross-section. This can be used to control the parameters of the positron sources for storage rings and colliders. Read More

We investigate the coherent electron-positron pair creation by high-energy photons in a periodically deformed single crystal with a complex base. The formula for the corresponding differential cross-section is derived for an arbitrary deformation field. The conditions are specified under which the influence of the deformation is considerable. Read More

We investigate the coherent bremsstrahlung by relativistic electrons in a single crystal excited by hypersonic vibrations. The formula for the corresponding differential cross-section is derived in the case of a sinusoidal wave. The conditions are specified under which the influence of the hypersound is essential. Read More

The influence of hypersonic waves excited in a single crystal is investigated on the process of electron-positron pair creation by high-energy photons. The coherent part of the corresponding differential cross-section is derived as a function of the amplitude and wave number of the hypersound. The values of the parameters are specified for which the latter affects remarkably on the pair creation cross-section. Read More

1999Jul
Affiliations: 1Institute of Applied Problems in Physics, Armenia, 2Institute of Applied Problems in Physics, Armenia, 3Institute of Applied Problems in Physics, Armenia, 4Institute of Applied Problems in Physics, Armenia, 5Institute of Applied Problems in Physics, Armenia
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Radiation generated by the passage of a monoenergetic electron bunch above the surface wave excited in plane interface between homogeneous media with different dielectric constants is investigated. For the surface wave of general profile the radiation intensity is expressed via the radiated power from a single charge and bunch form factor. Various types of transverse and longitudinal distributions of electrons in the bunch have been considered including Gaussian, asymmetrical Gaussian, two Gaussian and rectangular distribution with asymmetrical exponential tails. Read More

The paper is devoted to the study of the influence of crystalline lattice distortions due to external excitations (acoustic vibrations, temperature gradient, etc.) on the Quasicerenkov radiation. Equations describing Quasicerenkov radiation of charged particles in distorted crystals are derived. Read More