Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://nuclphys.sinp.msu.ru/conf/lpp14/210809/Peshekhonov.pdf Äàòà èçìåíåíèÿ: Wed Sep 16 16:30:31 2009 Äàòà èíäåêñèðîâàíèÿ: Tue Oct 2 00:45:56 2012 Êîäèðîâêà:

"Helicity quark distributions from DIS and SIDIS measured in COMPASS"
D.Peshekhonov

JINR, Dubna
on behalf of the COMPASS collaboration

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COmmon NA58 experiment at CERN M u on a n d ~230 physicists from 11 countries Proton Apparatus for Czech Republic, Finland, France, Germany, India, Israel, Italy, Japan, Structure and Poland, Portugal and Russia Spectroscopy
· Muon program (2002-2007) Deep Inelastic Scattering (DIS) of polarized 160 GeV/c muons on polarized deuterons and protons · Hadron program (2008-2009) 190 GeV/c , K , p beams search for exotics in dif fractive excitation and central production, polarizability of , K
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COMPASS

LH C SPS

longitudinally polarised muon beam intensity: 2·10 µ/spill (4.8 sec/16.2 sec) momentum: 160 GeV/c longitudinally/transversely polarised target
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COMPASS spectrometer
µ wall E/HCAL2

µ wall E/HCAL1 RICH Target

SM2

- Two magnets: 1 Tm, 4.5 Tm; - Tracking (p>0.5 GeV/c): SciFi, Silicon, MicroMega, GEM, MWPC, DC, Straw;

SM1 µ
(P80%)
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- PID (RICH): ,K,p; - Electromagnetic and Hadron Calorimeters; - 2(3) cells pol.target: 6 LiD(50%) & NH 3(90%)
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Spin of the nucleon

1 S N = ­ = ½ + G + L q+ L 2

{
g

Naive view: = uv + d v = 1

Complete description :
· = u + d + s (for q and q) · G · orbital angular momenta

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Deep inelastic scattering
Kinematical variables: Q² = -q² x = Q²/2M = E- E' y = /E
µ h N h h h

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Deep inelastic scattering
· quark densities in QPM: q(x) = q(x) + q(x) q(x) = q(x) - q(x) · Longitudinal double-spin asymmetry: · Longitudinal spin asymmetry N: · Cross-sections and · Structure functions: Structure functions:
D ­ depolarization factor of

· Structure functions and PDF:

· Asymmetry A and structure function g: g A F

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Asymmetry measurement
· to be measured: · measured values: · flux normalization: · acceptance: (constant ratio) · double ratio method:
solve for Aexp (2
nd

Spin rotation every 8h

order equation)

minimization of bias

· experimental asymmetry:

A

exp

=p



pT f A



p ,p T - beam and target polarization f - dilution factor
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Structure functions g and g

d

p

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Structure functions g

NS

Systematic error: · (Pb) is dominant : 5% ±0.065 · 6 LiD: 7% due to f and Pt ±0.041 · NH 3 : 3% due to f and Pt ±0.056
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Full flavor separation analysis with LO QCD fit

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Proton and deuteron asymmetries A
· Kinematic 2 2 Q > 1 GeV 0 .1 < y < 0 .9 0 .0 0 4 < x < 0 .7

· Asymmetries of identified hadrons were measured o n ly b y COMPASS and HERMES

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Proton and deuteron asymmetries A
· Kinematic 2 2 Q > 1 GeV 0 .1 < y < 0 .9 0 .0 0 4 < x < 0 .7

· Asymmetries of identified hadrons were measured o n ly b y COMPASS and HERMES

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o MRST04 (for unpol.PDFs) and DSS (for FFs); o Good agreement with global fit exept s

In c l + K+ K

Statistic (·10 ) Proton deuteron 9 2 ,5 1 3 5 ,1 1 3 ,3 2 2 ,8 11,8 2 0 ,5 3 ,9 4 ,8 2 ,6 3 ,3

6

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Flavor symmetry breaking of the light sea

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Conclusion
· All COMPASS data with deuteron(2002-2006) and proton(2007) targets have been processed and analyzed; · g was obtained from combined analysis of proton and deuteron data g A/g V = 1.30 ± 0.07(stat) ± 0.10(syst) confirm the validity of Bjorken sum rule; · Full flavor separation analysis with LO QCD fit was done: o Good agreement of non-strange PDFs with results of previous QCD fits; o Shape of s(x) disagree significantly with previous fits; o Flavor asymmetry of the light sea quarks is observed. Spin budget of the nucleon · Contribution of quarks to the nucleon spin is well fixed by inclusive data = 0.30 ± 0.01 ± 0.02 (Q²=3 GeV²); · QCD fit provides indirect way to determine G: | G| < 0.2Â0.3
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Spires

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LH C SPS

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LH C SPS

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