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Search Results: 1 - 10 of 325258 matches for " S. Danagoulian "
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Observation of coherent $π^0$ electroproduction on deuterons at large momentum transfer
E. Tomasi-Gustafsson,L. Bimbot,S. Danagoulian,K. Gustafsson,D. Mack,H. Mrktchyan,M. P. Rekalo
Physics , 2003, DOI: 10.1134/1.1634323
Abstract: The first experimental results for coherent $\pi^0$-electroproduction on the deuteron, $e+d\to e+d +\pi^0$, at large momentum transfer, are reported. The experiment was performed at Jefferson Laboratory at an incident electron energy of 4.05 GeV. A large pion production yield has been observed in a kinematical region for 1.1$
Compton Scattering Cross Section on the Proton at High Momentum Transfer
A. Danagoulian,V. H. Mamyan,M. Roedelbronn,the Hall A Collaboration
Physics , 2007, DOI: 10.1103/PhysRevLett.98.152001
Abstract: Cross-section values for Compton scattering on the proton were measured at 25 kinematic settings over the range s = 5-11 and -t = 2-7 GeV2 with statistical accuracy of a few percent. The scaling power for the s-dependence of the cross section at fixed center of mass angle was found to be 8.0 +/ 0.2, strongly inconsistent with the prediction of perturbative QCD. The observed cross-section values are in fair agreement with the calculations using the handbag mechanism, in which the external photons couple to a single quark.
Neutron Beam Effects on Spin Exchange Polarized He-3
M. Sharma,E. Babcock,K. H. Andersen,L. Barron-Palos,M. Becker,S. Boag,W. C. Chen,T. E. Chupp,A. Danagoulian,T. R. Gentile,A. Klein,S. Penttila,A. Petoukhov,T. Soldner,E. R. Tardiff,T. G. Walker,W. S. Wilburn
Physics , 2008, DOI: 10.1103/PhysRevLett.101.083002
Abstract: We have observed depolarization effects when high intensity cold neutron beams are incident on alkali-metal-spin-exchange polarized He-3 cells used as neutron spin filters. This was first observed as a reduction of the maximum attainable He-3 polarization and was attributed to a decrease of alkali-metal polarization, which led us to directly measure alkali-metal polarization and spin relaxation over a range of neutron fluxes at LANSCE and ILL. The data reveal a new alkali-metal spin-relaxation mechanism that approximately scales as the square root of the neutron capture-flux density incident on the cell. This is consistent with an effect proportional to the recombination-limited ion concentration, but is much larger than expected from earlier work.
Deuteron Electro-Disintegration at Very High Missing Momenta
W. U. Boeglin,M. K. Jones,K. Aniol,A. Asaturyan,H. Baghdasaryan,F. Benmokhtar,H. Bitao,S. Danagoulian,D. Day,D. Gaskell,D. Higinbotham,G. Huber,S. Jeschonnek,N. Kalantarians,P. E. Markowitz,A. Mkrtchyan,H. Mkrtchyan,E. Piasetzky,A. Puckett,B. A. Raue,J. Reinhold,G. Ron,M. Sargsian,R. Shneor,G. Smith,R. Subedi,V. Tadevosyan,J. W. Van Orden,F. R. Wesselmann
Physics , 2014,
Abstract: We propose to measure the D(e,e'p) cross section at $Q^2 = 4.25$ (GeV/c)$^2$ and $x_{bj} = 1.35$ for missing momenta ranging from $p_m = 0.5$ GeV/c to $p_m = 1.0$ GeV/c expanding the range of missing momenta explored in the Hall A experiment (E01-020). At these energy and momentum transfers, calculations based on the eikonal approximation have been shown to be valid and recent experiments indicated that final state interactions are relatively small and possibly independent of missing momenta. This experiment will provide for the first time data in this kinematic regime which are of fundamental importance to the study of short range correlations and high density fluctuations in nuclei. The proposed experiment could serve as a commissioning experiment of the new SHMS together with the HMS in Hall C. A total beam time of 21 days is requested.
Quasifree Lambda, Sigma^0, and Sigma^- electroproduction from 1,2H, 3,4He, and carbon
F. Dohrmann,A. Ahmidouch,C. S. Armstrong,J. Arrington,R. Asaturyan,S. Avery,K. Bailey,H. Bitao,H. Breuer,D. S. Brown,R. Carlini,J. Cha,N. Chant,E. Christy,A. Cochran,L. Cole,J. Crowder,S. Danagoulian,M. Elaasar,R. Ent,H. Fenker,Y. Fujii,L. Gan,K. Garrow,D. F. Geesaman,P. Gueye,K. Hafidi,W. Hinton,H. Juengst,C. Keppel,Y. Liang,J. H. Liu,A. Lung,D. Mack,P. Markowitz,J. Mitchell,T. Miyoshi,H. Mkrtchyan,S. K. Mtingwa,B. Mueller,G. Niculescu,I. Niculescu,D. Potterveld,B. A. Raue,P. E. Reimer,J. Reinhold,J. Roche,M. Sarsour,Y. Sato,R. E. Segel,A. Semenov,S. Stepanyan,V. Tadevosyan,S. Tajima,L. Tang,A. Uzzle,S. Wood,H. Yamaguchi,C. Yan,L. Yuan,B. Zeidman,M. Zeier,B. Zihlmann
Physics , 2007, DOI: 10.1103/PhysRevC.76.054004
Abstract: Kaon electroproduction from light nuclei and hydrogen, using 1H, 2H, 3He, 4He, and Carbon targets has been measured at Jefferson Laboratory. The quasifree angular distributions of Lambda and Sigma hyperons were determined at Q^2= 0.35(GeV/c)^2 and W= 1.91GeV. Electroproduction on hydrogen was measured at the same kinematics for reference.
Neutral Pion Electroproduction in the Resonance Region at High $Q^2$
A. N. Villano,P. Stoler,P. E. Bosted,S. H. Connell,M. M. Dalton,M. K. Jones,V. Kubarovsky,G. S Adams,A. Ahmidouch,J. Arrington,R. Asaturyan,O. K. Baker,H. Breuer,M. E. Christy,S. Danagoulian,D. Day,J. A. Dunne,D. Dutta,R. Ent,H. C. Fenker,V. V. Frolov,L. Gan,D. Gaskell,W. Hinton,R. J. Holt,T. Horn,G. M. Huber,K. Joo,N. Kalantarians,C. E. Keppel,Y. Li,A. Lung,D. Mack,S. Malace,P. Markowitz,D. G. Meekins,H. Mkrtchyan,J. Napolitano,G. Niculescu,I. Niculescu,D. H. Potterveld,Paul E. Reimer,J. Reinhold,J. Roche,S. E. Rock,G. R. Smith,S. Stepanyan,V. Tadevosyan,V. Tvaskis,M. Ungaro,A. Uzzle,S. Vidakovic,F. R. Wesselmann,B. Wojtsekhowski,S. A. Wood,L. Yuan,X. Zheng,H. Zhu
Physics , 2009, DOI: 10.1103/PhysRevC.80.035203
Abstract: The process $ep \to e^{\prime}p^{\prime}\pi^0$ has been measured at $Q^2$ = 6.4 and 7.7 GeV/c$^2$)$^2$ in Jefferson Lab's Hall C. Unpolarized differential cross sections are reported in the virtual photon-proton center of mass frame considering the process $\gamma^{\ast}p \to p^{\prime}\pi^0$. Various details relating to the background subtractions, radiative corrections and systematic errors are discussed. The usefulness of the data with regard to the measurement of the electromagnetic properties of the well known $\Delta(1232)$ resonance is covered in detail. Specifically considered are the electromagnetic and scalar-magnetic ratios $R_{EM}$ and $R_{SM}$ along with the magnetic transition form factor $G_M^{\ast}$. It is found that the rapid fall off of the $\Delta(1232)$ contribution continues into this region of momentum transfer and that other resonances
A New Measurement of the $π^0$ Radiative Decay Width
I. Larin,D. McNulty,E. Clinton,P. Ambrozewicz,D. Lawrence,I. Nakagawa,Y. Prok,A. Teymurazyan,A. Ahmidouch,A. Asratyan,K. Baker,L. Benton,A. M. Bernstein,V. Burkert,P. Cole,P. Collins,D. Dale,S. Danagoulian,G. Davidenko,R. Demirchyan,A. Deur,A. Dolgolenko,G. Dzyubenko,R. Ent,A. Evdokimov,J. Feng,M. Gabrielyan,L. Gan,A. Gasparian,S. Gevorkyan,A. Glamazdin,V. Goryachev,V. Gyurjyan,K. Hardy,J. He,M. Ito,L. Jiang,D. Kashy,M. Khandaker,P. Kingsberry,A. Kolarkar,M. Konchatnyi,A. Korchin,W. Korsch,S. Kowalski,M. Kubantsev,V. Kubarovsky,X. Li,P. Martel,V. Matveev,B. Mecking,B. Milbrath,R. Minehart,R. Miskimen,V. Mochalov,S. Mtingwa,S. Overby,E. Pasyuk,M. Payen,R. Pedroni,B. Ritchie,T. E. Rodrigues,C. Salgado,A. Shahinyan,A. Sitnikov,D. Sober,S. Stepanyan,W. Stephens,J. Underwood,A. Vasiliev,V. Vishnyakov,M. Wood,S. Zhou
Physics , 2010, DOI: 10.1103/PhysRevLett.106.162303
Abstract: High precision measurements of the differential cross sections for $\pi^0$ photoproduction at forward angles for two nuclei, $^{12}$C and $^{208}$Pb, have been performed for incident photon energies of 4.9 - 5.5 GeV to extract the ${\pi^0 \to \gamma\gamma}$ decay width. The experiment was done at Jefferson Lab using the Hall B photon tagger and a high-resolution multichannel calorimeter. The ${\pi^0 \to \gamma\gamma}$ decay width was extracted by fitting the measured cross sections using recently updated theoretical models for the process. The resulting value for the decay width is $\Gamma{(\pi^0 \to \gamma\gamma)} = 7.82 \pm 0.14 ~({\rm stat.}) \pm 0.17 ~({\rm syst.}) ~{\rm eV}$. With the 2.8% total uncertainty, this result is a factor of 2.5 more precise than the current PDG average of this fundamental quantity and it is consistent with current theoretical predictions.
Hypernuclear Spectroscopy using the (e,e'K+) Reaction
L. Yuan,M. Sarsour,T. Miyoshi,Z. Zhu,A. Ahmindouch,D. Androic,T. Angelescu,R. Asaturyan,S. Avery,O. K. Baker,I. Betovic,H. Breuer,R. Carlini,J. Cha,R. Chrien M. Christy,L. Cole,S. Danagoulian,D. Dehnhard,M. Elaasar,A. Empl,R. Ent,H. Fenker,Y. Fujii,M. Furic,L. Gan,K. Garrow,A. Gasparian,P. Gueye,M. harvey,O. Hashimoto,W. Hinton,B. Hu,E. Hungerford,C. Jackson,K. Johnston,H. Juengst,C. Keppel,K. Lan,Y. Liang,V. P. Likhachev,J. H. Liu,D. Mack,A. Margaryan,P. markowitz,H. Mkrtchyan,S. N. Nakamura,T. Petkovic,J. Reinhold,J. Roche,Y. Sato,R. Sawafta,N. Simicevic,G. Smith,S. Stepanyan,V. Tadevosyan,T. Takahashi,K. Tanida,L. Tang,M. Ukai,A. Uzzle,W. Vulcan,S. Wells,S. Wood,G. Xu,H. Yamaguchi,C. Yan
Physics , 2004, DOI: 10.1103/PhysRevC.73.044607
Abstract: A pioneering experiment in Lambda hypernuclear spectroscopy, undertaken at the Thomas Jefferson National Accelerator Facility (Jlab), was recently reported. The experiment used the high- precision, continuous electron beam at Jlab, and a special arrangement of spectrometer magnets to measure the spectrum from {nat}C and 7Li targets using the (e,e' K+)reaction. The 12B hypernuclear spectrum was previously published. This experiment is now reported in more detail, with improved results for the 12B hypernuclear spectrum. In addition, unpublished results of the 7He hypernuclear spectrum are also shown. This later spectrum indicates the need for a more detailed few-body calculation of the hypernucleus and the reaction process. The success of this experiment demonstrates that the (e,e'K+) reaction can be effectively used as a high resolution tool to study hypernuclear spectra, ant its use should be vigorously pursued.
Probing Quark-Gluon Interactions with Transverse Polarized Scattering
K. Slifer,O. A. Rondon,A. Aghalaryan,A. Ahmidouch,R. Asaturyan,F. Bloch,W. Boeglin,P. Bosted,C. Carasco,R. Carlini,J. Cha,J. P. Chen,M. E. Christy,L. Cole,L. Coman,D. Crabb,S. Danagoulian,D. Day,J. Dunne,M. Elaasar,R. Ent,H. Fenker,E. Frlez,D. Gaskell,L. Gan,J. Gomez,B. Hu,J. Jourdan,M. K. Jones,C. Keith,C. E. Keppel,M. Khandaker,A. Klein,L. Kramer,Y. Liang,J. Lichtenstadt,R. Lindgren,D. Mack,P. McKee,D. McNulty,D. Meekins,H. Mkrtchyan,R. Nasseripour,I. Niculescu,K. Normand,B. Norum,D. Pocanic,Y. Prok,B. Raue,J. Reinhold,J. Roche,D. Kiselev,N. Savvinov,B. Sawatzky,M. Seely,I. Sick,C. Smith,G. Smith,S. Stepanyan,L. Tang,S. Tajima,G. Testa,W. Vulcan,K. Wang,G. Warren,F. R. Wesselmann,S. Wood,C. Yan,L. Yuan,J. Yun,M. Zeier,H. Zhu
Physics , 2008, DOI: 10.1103/PhysRevLett.105.101601
Abstract: We have extracted QCD matrix elements from our data on double polarized inelastic scattering of electrons on nuclei. We find the higher twist matrix element \tilde{d_2}, which arises strictly from quark- gluon interactions, to be unambiguously non zero. The data also reveal an isospin dependence of higher twist effects if we assume that the Burkhardt-Cottingham Sum rule is valid. The fundamental Bjorken sum rule obtained from the a0 matrix element is satisfied at our low momentum transfer.
Nuclear Targets for a Precision Measurement of the Neutral Pion Radiative Width
P. Martel,E. Clinton,R. McWilliams,D. Lawrence,R. Miskimen,A. Ahmidouch,P. Ambrozewicz,A. Asratyan,K. Baker,L. Benton,A. Bernstein,P. Cole,P. Collins,D. Dale,S. Danagoulian,G. Davidenko,R. Demirchyan,A. Deur,A. Dolgolenko,G. Dzyubenko,A. Evdokimov,J. Feng,M. Gabrielyan,L. Gan,A. Gasparian,O. Glamazdin,V. Goryachev,V. Gyurjyan,K. Hardy,M. Ito,M. Khandaker,P. Kingsberry,A. Kolarkar,M. Konchatnyi,O. Korchin,W. Korsch,S. Kowalski,M. Kubantsev,V. Kubarovsky,I. Larin,V. Matveev,D. McNulty,B. Milbrath,R. Minehart,V. Mochalov,S. Mtingwa,I. Nakagawa,S. Overby,E. Pasyuk,M. Payen,R. Pedroni,Y. Prok,B. Ritchie,C. Salgado,A. Sitnikov,D. Sober,W. Stephens,A. Teymurazyan,J. Underwood,A. Vasiliev,V. Verebryusov,V. Vishnyakov,M. Wood
Physics , 2008, DOI: 10.1016/j.nima.2009.09.063
Abstract: A technique is presented for precision measurements of the area densities, density * T, of approximately 5% radiation length carbon and 208Pb targets used in an experiment at Jefferson Laboratory to measure the neutral pion radiative width. The precision obtained in the area density for the carbon target is +/- 0.050%, and that obtained for the lead target through an x-ray attenuation technique is +/- 0.43%.
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