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Search Results: 1 - 10 of 50507 matches for " Y. Prok "
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Measurement of the $x$- and $Q^2$-Dependence of the Asymmetry $A_1$ on the Nucleon
K. V. Dharmawardane,S. E. Kuhn,P. Bosted,Y. Prok,for the CLAS collaboration
Physics , 2006, DOI: 10.1016/j.physletb.2006.08.011
Abstract: We report results for the virtual photon asymmetry $A_1$ on the nucleon from new Jefferson Lab measurements. The experiment, which used the CEBAF Large Acceptance Spectrometer and longitudinally polarized proton ($^{15}$NH$_3$) and deuteron ($^{15}$ND$_3$) targets, collected data with a longitudinally polarized electron beam at energies between 1.6 GeV and 5.7 GeV. In the present paper, we concentrate on our results for $A_1(x,Q^2)$ and the related ratio $g_1/F_1(x,Q^2)$ in the resonance and the deep inelastic regions for our lowest and highest beam energies, covering a range in momentum transfer $Q^2$ from 0.05 to 5.0 GeV$^2$ and in final-state invariant mass $W$ up to about 3 GeV. Our data show detailed structure in the resonance region, which leads to a strong $Q^2$--dependence of $A_1(x,Q^2)$ for $W$ below 2 GeV. At higher $W$, a smooth approach to the scaling limit, established by earlier experiments, can be seen, but $A_1(x,Q^2)$ is not strictly $Q^2$--independent. We add significantly to the world data set at high $x$, up to $x = 0.6$. Our data exceed the SU(6)-symmetric quark model expectation for both the proton and the deuteron while being consistent with a negative $d$-quark polarization up to our highest $x$. This data setshould improve next-to-leading order (NLO) pQCD fits of the parton polarization distributions.
Quark-Hadron Duality in Spin Structure Functions g1p and g1d
P. E. Bosted,K. V. Dharmawardane,G. E. Dodge,T. A. Forest,S. E. Kuhn,Y. Prok et al.
Physics , 2006, DOI: 10.1103/PhysRevC.75.035203
Abstract: New measurements of the spin structure functions of the proton and deuteron g1p(x,Q2) and g1d(x,Q2) in the nucleon resonance region are compared with extrapolations of target-mass-corrected next-to-leading-order (NLO) QCD fits to higher energy data. Averaged over the entire resonance region (W<2 GeV), the data and QCD fits are in good agreement in both magnitude and Q2 dependence for Q2>1.7 GeV2. This global duality appears to result from cancellations among the prominent local resonance regions: in particular strong sigma{3/2} contributions in the Delta(1232) region appear to be compensated by strong sigma{1/2} contributions in the resonance region centered on 1.5 GeV. These results are encouraging for the extension of NLO QCD fits to lower W and Q2 than have been used previously.
Moments of the Spin Structure Functions g_1^p and g_1^d for 0.05 < Q^2 < 3.0 GeV^2
Y. Prok,P. Bosted,V. D. Burkert,A. Deur,K. V. Dharmawardane,G. E. Dodge,K. A. Griffioen,S. E. Kuhn,R. Minehart,the CLAS Collaboration
Physics , 2008, DOI: 10.1016/j.physletb.2008.12.063
Abstract: The spin structure functions g_1 for the proton and the deuteron have been measured over a wide kinematic range in x and Q2 using 1.6 and 5.7 GeV longitudinally polarized electrons incident upon polarized NH_3 and ND_3 targets at Jefferson Lab. Scattered electrons were detected in the CEBAF Large Acceptance Spectrometer, for 0.05 < Q^2 < 5 GeV^2 and W < 3 GeV. The first moments of g_1 for the proton and deuteron are presented -- both have a negative slope at low Q^2, as predicted by the extended Gerasimov-Drell-Hearn sum rule. The first result for the generalized forward spin polarizability of the proton gamma_0^p is also reported. This quantity shows strong Q^2 dependence at low Q^2, while Q^6\gamma_0^p seems to flatten out at the highest Q^2 accessed by our experiment. Although the first moments of g_1 are consistent with Chiral Perturbation Theory (ChPT) calculations up to approximately Q^2 = 0.06 GeV^2, a significant discrepancy is observed between the \gamma_0^p data and ChPT for gamma_0^p, even at the lowest Q2.
Experimental study of isovector spin sum rules
A. Deur,P. Bosted,V. Burkert,D. Crabb,V. Dharmawardane,G. E. Dodge,T. A. Forest,K. A. Griffioen,S. E. Kuhn,R. Minehart,Y. Prok
Physics , 2008, DOI: 10.1103/PhysRevD.78.032001
Abstract: We present the Bjorken integral extracted from Jefferson Lab experiment EG1b for $0.05
High precision determination of the $Q^2$-evolution of the Bjorken Sum
A. Deur,Y. Prok,V. Burkert,D. Crabb,F. -X. Girod,K. A. Griffioen,N. Guler,S. E. Kuhn,N. Kvaltine
Physics , 2014, DOI: 10.1103/PhysRevD.90.012009
Abstract: We present a significantly improved determination of the Bjorken Sum for 0.6$\leq Q^{2}\leq$4.8 GeV$^{2}$ using precise new $g_{1}^{p}$ and $g_{1}^{d}$ data taken with the CLAS detector at Jefferson Lab. A higher-twist analysis of the $Q^{2}$-dependence of the Bjorken Sum yields the twist-4 coefficient $f_{2}^{p-n}=-0.064 \pm0.009\pm_{0.036}^{0.032}$. This leads to the color polarizabilities $\chi_{E}^{p-n}=-0.032\pm0.024$ and $\chi_{B}^{p-n}=0.032\pm0.013$. The strong force coupling is determined to be $\alpha_{s}^{\overline{\mbox{ MS}}}(M_{Z}^{2})=0.1124\pm0.0061$, which has an uncertainty a factor of 1.5 smaller than earlier estimates using polarized DIS data. This improvement makes the comparison between $\alpha_{s}$ extracted from polarized DIS and other techniques a valuable test of QCD.
Measurement of Strange Quark Contributions to the Vector Form Factors of the Proton at Q**2=0.22 (GeV/c)**2
S. Baunack,K. Aulenbacher,D. Balaguer Ríos,L. Capozza,J. Diefenbach,B. Gl?ser,D. v. Harrach,Y. Imai,E. M. Kabu?,R. Kothe,J. H. Lee,H. Merkel,M. C. Mora Espí,U. Müller,E. Schilling,G. Stephan,C. Weinrich,J. Arvieux,M. A. El-Yakoubi,R. Kunne,F. E. Maas,M. Morlet,S. Ong,J. van de Wiele,S. Kowalski,Y. Prok,S. Taylor
Physics , 2009, DOI: 10.1103/PhysRevLett.102.151803
Abstract: A new measurement of the parity violating asymmetry in elastic electron scattering on hydrogen at backward angles and at a four momentum transfer of Q^2=0.22 (GeV/c)^2 is reported here. The measured asymmetry is A_LR=(-17.23 +- 0.82_stat +-0.89_syst) ppm. The Standard Model prediction assuming no strangeness is A_0=(-15.87 +- 1.22) ppm. In combination with previous results from measurements at forward angles, it it possible to disentangle for the first time the strange electric and magnetic form factors at this momentum transfer, G_E^s(0.22)=0.050 +- 0.038 +- 0.019 and G_M^s(0.22)=-0.14 +- 0.11 +- 0.11.
Equality in Laszlo Fejes Toth's triangle bound for hyperbolic surfaces
C. Barvard,K. J. Boroczky,B. Ormos,I. Prok,L. Vena,G. Wintsche
Mathematics , 2012,
Abstract: For k>6, we determine the minimal area of a compact hyperbolic surface, and an oriented compact hyperbolic surface that can be tiled by embedded regular triangles of angle 2\pi/k. Based on this, all the cases of equality in Laszlo Fejes Toth's triangle bound for hyperbolic surfaces are described.
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.
Polarization Transfer in Wide-Angle Compton Scattering and Single-Pion Photoproduction from the Proton
C. Fanelli,E. Cisbani,D. J. Hamilton,G. Salme,B. Wojtsekhowski,A. Ahmidouch,J. R. M. Annand,H. Baghdasaryan,J. Beaufait,P. Bosted,E. J. Brash,C. Butuceanu,P. Carter,E. Christy,E. Chudakov,S. Danagoulian,D. Day,P. Degtyarenko,R. Ent,H. Fenker,M. Fowler,E. Frlez,D. Gaskell,R. Gilman,T. Horn,G. M. Huber,C. W. de Jager,E. Jensen,M. K. Jones,A. Kelleher,C. Keppel,M. Khandaker,M. Kohl,G. Kumbartzki,S. Lassiter,Y. Li,R. Lindgren,H. Lovelace,W. Luo,D. Mack,V. Mamyan,D. J. Margaziotis,P. Markowitz,J. Maxwell,G. Mbianda,D. Meekins,M. Meziane,J. Miller,A. Mkrtchyan,H. Mkrtchyan,J. Mulholland,V. Nelyubin,L. Pentchev,C. F. Perdrisat,E. Piasetzky,Y. Prok,A. J. R. Puckett,V. Punjabi,M. Shabestari,A. Shahinyan,K. Slifer,G. Smith,P. Solvignon,R. Subedi,F. R. Wesselmann,S. Wood,Z. Ye,X. Zheng
Physics , 2015, DOI: 10.1103/PhysRevLett.115.152001
Abstract: Wide-angle exclusive Compton scattering and single-pion photoproduction from the proton have been investigated via measurement of the polarization transfer from a circularly polarized photon beam to the recoil proton. The wide-angle Compton scattering polarization transfer was analyzed at an incident photon energy of 3.7~GeV at a proton scattering angle of \cma$= 70^\circ$. The longitudinal transfer \KLL, measured to be $0.645 \pm 0.059 \pm 0.048$, where the first error is statistical and the second is systematic, has the same sign as predicted for the reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton. However, the observed value is $\sim$3~times larger than predicted by the generalized-parton-distribution-based calculations, which indicates a significant unknown contribution to the scattering amplitude.
Proton Spin Structure in the Resonance Region
RSS Collaboration,F. R. Wesselmann,K. Slifer,S. Tajima,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,L. Gan,D. Gaskell,J. Gomez,B. Hu,M. K. Jones,J. Jourdan,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. Rohe,O. A. Rondon,N. Savvinov,B. Sawatzky,M. Seely,I. Sick,C. Smith,G. Smith,S. Stepanyan,L. Tang,G. Testa,W. Vulcan,K. Wang,G. Warren,S. Wood,C. Yan,L. Yuan,J. Yun,M. Zeier,H. Zhu
Physics , 2006, DOI: 10.1103/PhysRevLett.98.132003
Abstract: We have examined the spin structure of the proton in the region of the nucleon resonances (1.085 GeV < W < 1.910 GeV) at an average four momentum transfer of Q^2 = 1.3 GeV^2. Using the Jefferson Lab polarized electron beam, a spectrometer, and a polarized solid target, we measured the asymmetries A_parallel and A_perp to high precision, and extracted the asymmetries A_1 and A_2, and the spin structure functions g_1 and g_2. We found a notably non-zero A_perp, significant contributions from higher-twist effects, and only weak support for polarized quark--hadron duality.
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