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4 Summary Since the end of data-taking in 2007, the HERMES Collaboration has continued in refining the quality of and analyzing data. The large statistics of inclusive DIS events collected by HERMES with hydrogen and deuterium targets allowed to perform a new measurement of the structure function F2(x) for proton and deuteron. The data cover a new still unexplored region and are in agreement with world data in the overlap region. A measurement of the spin-dependent structure function of the proton g2(x) is performed. This is the first measurement of HERMES where both, longitudinal polarization of the beam and transverse polarization of the target are important. The results are in agreement with the most accurate data obtained by the E155 experiment and do not show any evidence, within the statistical accuracy, of a contribution of the twist-3 part ¯g2(x). A search of the two-photon exchange effects using the transversely polarized hydrogen target gave no evidence within the uncertainty, at the level of 10 −3 . The final result on the extraction of the Sivers amplitudes from semi-inclusive production of pions and charged kaons using unpolarized lepton beam and transversely polarized hydrogen target was obtained. The results obtained based on a small part of the collected statistics are confirmed on the full data sample and new results on the amplitudes for production of neutral pions and charged kaons are presented. The amplitudes for positive kaons is larger then for positive pions. Azimuthal asymmetries for semi-inclusive production of positive and negative hadrons with unpolarized hydrogen and deuterium targets were studied. The different behaviour of positive and negative hadrons can be considered as an evidence of a non-zero Boer-Mulders distribution function. Strange quark distributions, S(x) andΔS(x), were measured using production of charged kaons off deuterium target. The measured shape of xS(x) is in a contradiction with known parameterizations. The strange helicity distribution is consistent with zero. References [1] J. Ashman et al., Phys.Lett. B 206 (1988) 364. [2] K. Ackerstaff et al., NIM A 417 (1998) 230. [3] A. Airapetian et al., Phys.Rev. D75(2007) 012007. [4] B. Adeva et al., Phys.Rev. D58(1998) 112001. [5] D. Gabbert, L. De Nardo, arXiv:0708.3196. [6] A. Airapetian et al., arXiv:0907.5369. [7] A. Airapetian et al., Phys.Rev.Lett. 94 (2005) 012002. [8] J.C. Colins, Nucl.Phys. B 396 (1993) 161. [9] D.W. Sivers, Phys.Rev. D41(1990) 83. [10] A. Airapetian et al., Phys.Rev.Lett. 103 (2009) 152002. [11] A. Bacchetta et al., JHEP 0702 (2007) 093. [12] A. Airapetian et al., Phys.Lett. B 666 (2008) 446. 228
NLO QCD PREDICTIONS FOR GLUON POLARIZATION FROM OPEN-CHARM ASYMMETRIES MEASURED AT COMPASS Krzysztof Kurek † Andrzej So̷ltan Institute for Nuclear Studies † E-mail: kurek@fuw.edu.pl Abstract Recently published by the COMPASS Collaboration result on gluon polarization, ΔG/G, from the open-charm channel has been obtained in the LO QCD approximation. The NLO QCD corrections to the analyzing power for the Photon- Gluon Fusion process are calculated in the COMPASS kinematical domain. The method based on the LO QCD Monte-Carlo generator with Parton Shower is proposed to simulate Phase Space for the NLO QCD processes. This approach can be easily implemented in the weighted method for estimation of gluon polarization, used in the COMPASS analysis. The new result for the gluon polarization in the NLO QCD approximation, based on published asymmetries for open-charm channel from COMPASS, is shown. The proposed method is compared with the approach where events are generated from uniformly distributed kinematical variables and then weighted by calculated NLO QCD cross section for Photon-Gluon Fusion process. This allows to control the potential bias related to the non-properly treated Phase Space for NLO QCD processes in the LO QCD Monte Carlo with Parton Shower concept. 1 Introduction The COMPASS is a fixed target experiment at CERN laboratory. One of its goals is the direct measurement of the gluon polarization, important for understanding the spin structure of the nucleon. The experiment is using a 160 GeV polarized muon beam from SPS at CERN scattered off a polarized 6 LiD target [1]. In LO QCD approximation the only subprocess which probes gluons inside nucleon is Photon-Gluon Fusion (PGF). There are two ways allowing direct access to gluon polarisation via the PGF subprocess available in the COMPASS experiment: the open-charm channel where the events with reconstructed D 0 mesons are used and the production of two hadrons with relatively high-pT in the final state. The estimation of the gluon polarisation in the open-charm channel is much less Monte-Carlo (MC) dependent than in the two high-pT hadrons method, where the complicated background requires very good MC description of the data. On the other hand the statistical precision in high-pT hadrons method is much higher than in the open charm channel. To increase statistical precision the weighting method has been used in the open-charm analysis, recently published by COMPASS Collaboration [2]. The analysis has been performed in LO QCD approximation. The resolved photon contribution has been checked to be unimportant in the kinematical domain covered by COMPASS experiment. The estimation of the gluon 229
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XIII Advanced Research Workshop on
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ã�� [539.12.01 + 539.12 ... 14
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Analytic perturbation theory and pr
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Measurements of GEp/GMp to high Q 2
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WELCOME ADDRESS Alexei Sissakian Di
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he joined the group of prof. Przemy
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proton. Dividing these 90 ◦ cm p-
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p-p scattering angle fixed at exact
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tuning for each ring. The Workshop
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was only about 10 5 per second, but
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[10] E.F. Parker et al., Phys. Rev.
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MICROSCOPIC STERN-GERLACH EFFECT AN
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DeGrand-Miettinen model predicted P
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TOWARDS STUDY OF LIGHT SCALAR MESON
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104xdBR(φ--> π η 0 -1 γ )/dm, G
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RECURSIVE FRAGMENTATION MODEL WITH
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Figure 2: String decaying into pseu
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pT -distributions in the quark frag
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4 Inclusion of spin-1 mesons For a
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CONSTITUENT QUARK REST ENERGY AND W
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〈r 2 ch 〉≈1fm2 . Now with Eqs
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TOWARDS A MODEL INDEPENDENT DETERMI
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Common for the difference cross sec
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TRANSVERSITY GPDs FROM γN → πρ
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The scattering amplitude of the pro
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INFRARED PROPERTIES OF THE SPIN STR
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5 Acknowledgement B.I. Ermolaev is
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We shall call this model the “sec
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y f ν V = f l V = f u V = f d gz V
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2. We remind, that the celebrated G
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of the resonance A, θV � 39 o .
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• Right-handed EW currents. The c
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pesum- (p Entries 0 + pe)-(p-pe) Me
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CROSS SECTIONS AND SPIN ASYMMETRIES
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R(ρ) 5 4 3 2 1 0 2 3 4 5 6 7 8 9 1
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TWO-PHOTON EXCHANGE IN ELASTIC ELEC
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and depend on three parameters : fN
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O(αs) SPIN EFFECTS IN e + e −
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3 Polarization results for mq → 0
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Since one has (↑↓) pc Born =(
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Figure 1: A typical lowest order Fe
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sin φ S (π + ) A UT 1.0 0.8 0.6 0
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form the agreement with these data
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in settling this dynamical issue. G
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SPIN CORRELATIONS OF THE ELECTRON A
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the two-photon system equaling 1).
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ANOTHER NEW TRACE FORMULA FOR THE C
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Compare the gain of time and effort
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where the triplet and octet axial c
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[2] Y. Prok et al. [CLAS Collaborat
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Melosh rotations which boost the re
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ky �GeV� 0.4 0.2 0.0 �0.2 �
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[2] B. Pasquini, and S. Boffi, Phys
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The appearance of both |+〉 and |
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2.2 Intrinsic Transverse Motion Qua
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are still complex: for a given corr
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This last is required to complete t
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[16] P.G. Ratcliffe and O.V. Teryae
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Figure 1: a)[left] μpG p E /Gp M (
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4 Conclusion We introduced a simple
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√ δΔq8 x for Δq8 and γΔGx fo
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understanding of polarized light qu
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They are inverse powers of Q 2 kine
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accounts approximately for the TM a
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POTENTIAL FOR A NEW MUON g-2 EXPERI
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When the momentum increases (p >p0)
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EVOLUTION EQUATIONS FOR TRUNCATED M
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4 Perspectives Evolution equations
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NEW DEVELOPMENTS IN THE QUANTUM STA
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statistical approach compared to th
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POLARIZED HADRON STRUCTURE IN THE V
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g 3 A =Δuv(Q 2 ) − Δdv(Q 2 ), g
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AXIAL ANOMALIES, NUCLEON SPIN STRUC
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3. Vector current of strange quarks
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ORBITAL MOMENTUM EFFECTS DUE TO A L
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The elastic scattering S-matrix in
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IDENTIFICATION OF EXTRA NEUTRAL GAU
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for final l + l − events (l = μ,
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QUARK INTRINSIC MOTION AND THE LINK
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where wP = − m 2M 2 −p1 cos ω
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where g q 2x − ξ 1(x, pT )= πM2
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EXPERIMENTAL RESULTS
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01 00 11 01 01 01 00 11 01 01 01 00
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where C1, C2 and A1 - signals from
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Figure 1: Layout of experiment targ
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According to requirements of the de
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Electron energy is measured at ATLA
Page 180 and 181: Fig. 2 shows the results of the lon
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Page 184 and 185: cos 0φ C A φ cos C A cos 2φ C A
Page 186 and 187: 5 Summary HERMES has measured signi
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Page 190 and 191: was done in the interval ”−t”
Page 192 and 193: If we admit a non-zero quark transv
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Page 196 and 197: In figure 3 the expected errors on
Page 198 and 199: [12] A. V. Efremov and O. V. Teryae
Page 200 and 201: Figure 1: The COMPASS spectrometer.
Page 202 and 203: Comparing this formula to the inclu
Page 204 and 205: Figure 5: Comparison of COMPASS inc
Page 206 and 207: [9] B. Adeva et al. (SMC Coll.), Ph
Page 208 and 209: q T sin( φ-φ ) M AUT 0.14 0.12 0.
Page 210 and 211: proton beam is planned. References
Page 212 and 213: Run Year √ s (GeV) Polarization R
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Page 216 and 217: At √ s = 200 GeV, ALL(pp → π
Page 218 and 219: [6] D. de Florian, W. Vogelsang, an
Page 220 and 221: higher energies, where the cross se
Page 222 and 223: Figure 3: The experimental results
Page 224 and 225: kinematic range to low values of Bj
Page 226 and 227: 3 Semi-Inclusive DIS Collins and Si
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Page 234 and 235: Finally the COMPASS reconstruction
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Page 238 and 239: with only modern NN potential are r
Page 240 and 241: (a) (b) Figure 3: (a) T20 data take
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Page 244 and 245: As is seen in Fig. 1 values of the
Page 246 and 247: SEMI-INCLUSIVE DIS AND TRANSVERSE M
Page 248 and 249: The yellow band in Fig. 1 is the re
Page 250 and 251: At leading twist, a third asymmetry
Page 252 and 253: THE COMPLETION OF SINGLE-SPIN ASYMM
Page 254 and 255: A N , % 30 20 10 0 0 0.2 0.4 0.6 0.
Page 256 and 257: Unexpectedly large single spin asym
Page 258 and 259: THE GENERALIZED PARTON DISTRIBUTION
Page 260 and 261: , E) H ~ (H, I Im C 5 4 3 2 1 Q = 1
Page 262 and 263: Reducing to a common denominator (
Page 264 and 265: LAMBDA PHYSICS AT HERMES S. Belosto
Page 266 and 267: analysis was carried out reconstruc
Page 268 and 269: SPIN PHYSICS AT NICA A. Nagaytsev J
Page 270 and 271: original software packages (MC simu
Page 272 and 273: MEASUREMENTS OF TRANSVERSE SPIN EFF
Page 274 and 275: to “near-side” and “away-side
Page 276 and 277: THE FIRST STAGE OF POLARIZATION PRO
Page 278 and 279: In paper [12] the study was made of
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emphasis to increase the statistics
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Table 2: The parameters of the main
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POLARIZATION MEASUREMENTS IN PHOTOP
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With a polarized electron beam inci
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Figure 3: Preliminary helicity asym
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INVESTIGATION OF DP-ELASTIC SCATTER
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framework with the use of deuteron
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SPIN PHYSICS WITH CLAS Y. Prok 12,
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1.3 Flavor Decomposition of the Hel
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Γ p 1 0.15 0.125 0.1 0.075 0.05 0.
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The upcoming energy upgrade of Jeff
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y the nearly 1000 combined citation
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� R = −Pt/Pl τ(1 + ε)/2ε; he
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4 Results of GEp-III Experiment In
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6 Theoretical Developments The earl
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lz = 0 (along the direction of the
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models have recently been challenge
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[32] Chung P. L. and F. Coester, Ph
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48 ± 3% for two beams. The proton
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is constant with cos θ∗ , as exp
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In summary, we made measurements on
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angle between the direction of the
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The sensitivity of the data to the
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COMPASS could be converted into a f
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3.1.2 Beam charge and spin asymmetr
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contributions enter only beyond lea
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References [1] D. Mueller et al, Fo
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l’ l p q p h H (z) 1 h (x) 1 l l
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3. Data selection. The data selecti
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φ sin3 a 0.06 0.04 0.02 0 -0.02 -0
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TRANSVERSE SPIN AND MOMENTUM EFFECT
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model. Both the cos φh and the cos
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D cos φ A 0 -0.1 -0.2 -0.3 + h -2
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4.3 The Sivers asymmetry According
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[3] A. Airapetian et al. [HERMES co
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2. Delta-Sigma Experimental Set-up.
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6. Estimate of the count rate in tr
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2 Analysis Formalism Spin-dependent
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The MC production comprises three s
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6 High pT hadron pair analysis for
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[2] V. Y. Alexakhin et al. [COMPASS
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2 Towards polarized Antiprotons For
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4 Spin-Filtering Experiments at COS
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to test the theoretical models of t
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C1 C2 π CH1,2 CH3,4 CH5,6 111 000
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not even resemble the data behavior
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to the slope of the Rosenbluth plot
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The differential cross section of t
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with zero for all mass ranges, with
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more precise and dedicated measurem
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oth types of experiment results are
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is recorded, a good particle identi
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error of the extracted asymmetries
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2.6 Summary and Outlook The first d
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386
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PROTON BEAM POLARIZATION MEASUREMEN
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N A 0.06 0.05 0.04 0.03 0.02 0.01 0
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Intensity profile (arb. units) 1 0.
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[4] H. Okada et al., Proc. of the 1
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The amplitudes of the signals and t
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The following results has been obta
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interaction vanishes and a single Z
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an amorphous NH3 for low and high,
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and depends on a choice of � ℓ1
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3 The conditions for transparent sp
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where angles α and β are defined
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forward angles, where vector Ay and
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espectively. The open symbols repre
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RF dipole (transverse B): εBdl = 1
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i PV / PV i PV / PV 1 0.5 0 -0.5 -1
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The energies of the states Ψ1 −
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field P ≈ +1. If we add the trans
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econstruction provide more accurate
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y detector saturation from pC colli
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2 �p+ 8 He analyzing power measur
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3.3 Effect of valence neutrons on s
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i.e. n0(θ +2π) =n0(θ) . There ar
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w and ˙ɛ. For example, we use par
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436
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REGULARIZATION OF SOURCE OF THE KER
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The corresponding phase transition
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ABOUT SPIN PARTICLE SOLUTION IN BOR
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where the functions fi(s, η) must
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SPINDYNAMICS I.B. Pestov JINR, 1419
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State of hadron matter is defined t
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REMARK ON SPIN PRECESSION FORMULAE
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It is easy to see that for a (massi
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DYNAMICS OF SPIN IN NONSTATIC SPACE
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Schwinger gauge. Probably for the f
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DSPIN-09 WORKSHOP SUMMARY Jacques S
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to some preliminary results reporte
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A new measurement of the polarizati
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new NLO QCD parametrization of the
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Name (Institution, Town, Country) E
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