Victor Abramov SPIN-2005, XI International Workshop, Dubna, September 27 - October 1, 2005 Single Spin Asymmetry of Charged Hadron Production by 40 GeV/c polarized protons V.V. Abramov, P.I. Goncharov, A.Yu. Kalinin, A.V. Khmelnikov, A.V. Korablev, Yu.P. Korneev, А.V. Kostritsky, А.N. Krinitsyn, V.I. Kryshkin, A.A. Markov, V.V. Talov, L.K. Turchanovich, A.A. Volkov Institute for High Energy Physics, Protvino, Russia Single transverse spin asymmetries (A N ) were measured for reactions p + А с X, where с = , , K , K , p and p, in central and forward regions using 40 GeV/c IHEP polarized proton beam.
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Single Spin Asymmetry of Charged Hadron Production by 40 GeV/c polarized protons
Single Spin Asymmetry of Charged Hadron Production by 40 GeV/c polarized protons. V . V . Abramov, P . I . Goncharov, A.Yu. Kalinin, A . V . Khmelnikov, A . V . Korablev, Yu . P . Korneev, А .V . Kostritsky, А .N . Krinitsyn, V . I . Kryshkin, A . A . Markov, - PowerPoint PPT Presentation
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Victor AbramovSPIN-2005, XI International Workshop, Dubna, September 27 - October 1, 2005
Single Spin Asymmetry of Charged Hadron Production by 40 GeV/c polarized protons
In case of symmetric FODS position analyzing powers from two arms were averaged to cancel some systematic uncertainties.
Measurements have been performed at two signs of magnetic field B to reduce systematic errors.
Measurements have been performed at two values of magnetic field (B & B/2) to increase hadron momentum range and equalize statistics at different pT.
The presented results are based on 22.8M events, recorded in two runs in 2003 using carbon and copper targets.
Difference in mean coordinates for Up and Down beam polarizations
Beam coordinates are measured in each event by X and Y hodoscope planes.
The mean beam coordinates, averaged over spill time, have difference for UP and Down beam polarizations.
The cuts are applied to UP and Down beam coordinates to level their mean values and to remove false asymmetry.
False asymmetry due to difference in X or Y for Up and Down polarized beam
False asymmetry is minimal near maximum (plateau) of PT distribution.
We have to level UP and Down coordinates with 4 μm accuracy to have false asymmetry less than 0.002.
The remaining systematic uncertainty 0.04 is estimated from run to run AN variation and is added in quadrature to the statistical error.
Analyzing Power for p + A π+ X
There is no significantA-dependence of AN.
There is a breakdownin pT-dependence withmaximum near 2.5 GeV/c.
First π+ data for pT ≥ 2.2 GeV/c.
The AN breakdown at 2.5 GeV/c could indicate a transition to the pQCD regime, where AN 0.
Analyzing Power for p + A π– X
AN ≈ 0 for θcm ≈ 85o.
First π– data for pT ≥ 2.2 GeV/c.
There is no significantA-dependence of AN.
The measurements at other angles are required in order to disentangle the PT and xF dependences. We plan to do these measurements in future.
Analyzing Power for p + A K+ X
There is breakdownin pT-dependence near 2.2 GeV/c.
First K+ data for pT ≥ 1 GeV/c.
There is no significantA-dependence of AN.
There is similarity with π+ asymmetry. In both cases valence u-quark contributes to the hadron production.
Analyzing Power for p + A K– X
There is no significantA-dependence of AN.
First K– data for pT ≥ 1 GeV/c.
AN for K– data ≈ 0, as expected due to small sea quark polarization.
Analyzing Power for p + A p X
AN ≈ 0 for θcm ≈ 88o.
AN oscillates as a function of pT with minimum at 1.3 GeV/c and maximum near 2.2 GeV/c for θcm ≈ 50o.
First proton data for pT ≥ 1 GeV/c.
Data are consistent with other experiments, all of which have pT < 1 GeV/c and AN 0.
Analyzing Power for p + A p X
There is no significantA-dependence of AN.
First p data.
AN for p data ≈ 0, as expected due to small sea quark polarization.
AN for p + A π+ X at 104.4o
There is no significantA-dependence of AN.
There is no pT-dependence of AN.
AN 0.05 for pC and pCu.
First π+ data for θcm > 90o.
AN for p + A π─ X at 104.4o
There is no significantA-dependence of AN.
There is no pT-dependence of AN.
AN 0 for pC and pCu.
First π─ data for θcm > 90o.
AN for p + A p X at 108.2o
There is no significantA-dependence of AN.
AN 0 for pC and pCu.
First p data for θcm > 90o.
AN scaling for π+ production at high xF
At high energies and PT scaling is expected:
AN ~F(PT)[GA(XA–X0)-GB(XB –X0)]
XA = (XR + XF)/2 -u/s;
XB = (XR ─ XF)/2 -t/s;
X0 = 0.075NQ + 2NQMQ(1+cosθcm)/s
MQ= 0.3 GeV, quark mass. NQ=2 in π+
XS = XA – X0 ;
In forward region (θcm<50o) XB 0;
AN rises for XS > 0, where it shows a scaling behaviour.
AN scaling for π─ production at high xF
AN ~F(PT)[GA(XA–X0)-GB(XB–X0)]
X0 = 0.075NQ+2NQMQ(1+cosθcm)/s
XS = XA – X0;
AN start to rise at XS = 0;
Agreement with E925 for PT > 0.6 GeV/c.
Some AN dependence on angle (PT), target and energy is possible at PT below 0.6 GeV/c.
Other examples of AN scaling:
V.V.Abramov, Eur.Phys.J. C14(2000)427;
Physics of Atomic Nucl., 68(2005)385.
AN energy dependence for protons
AN ~F(PT)[GA(XA–X0)-GB(XB– X0)]
X0 = 0.075NQ+2NQMQ(1+cosθcm)/s
XS = XA – X0; NQ=3 for proton;
AN start to rise at XS = 0;
Agreement with E925 for PT > 0.6 GeV/c.
Some AN dependence on angle (PT), target and energy is possible at lower PT.
Summary
AN was measured for π +, π –, K+, K–, p̃ & protons at FODS-2 setup. The mean angle θcm was near 48o, 86o & 105o.
The data were obtained with pT up to 4 GeV/c in central region and with xF up to 0.7 in forward regions for pC & pCu collisions.
There is no significant A-dependence for AN. First data for K– & p̃ show near zero AN for pC & pCu collisions
as expected due to small sea quarks polarization. Breakdown in pT–dependence of analyzing powers for π +, K+ &
protons in pC & pCu collisions could indicate a transition to the pQCD regime above 2.5 GeV/c, where AN tends to zero.
The asymmetry for θcm = 105o is close to zero. Scaling behavior of AN in the forward region & pT > 0.6 GeV/c.
xF -dependence of AN for π+ and π─ production
AN energy dependence for protons
Dimensional SSA analysis and scaling
Scaling for large of s, -t и –u:AN = AN (PT/PT
h, PT/PTQ, MQ/s, xA, xB) (4)
PT < PTh 1/Rh 0.35 GeV (quarks are not seen inside
hadrons)PT
h < PT < PTQ (constituent quarks revealed)
PT > PTQ 3/RQ 2.7 ГэВ (transition to current quarks)
Scaling variables:xA = -u/s (xR + xF)/2 EC/EA
(in B rest frame) (5)xB = -t/s (xR – xF)/2 EC/EB (in A rest frame) (6)
Threshold energy (ETh) of hadron С in c.m.: ETh NQ[MQ + XMINs/2], (7)where NQ – number of quarks in С; XMIN – minimal momentum fraction carried by constituent quark Q.
Energy dependence of hadron C threshold energy (ETh) in c.m.
ETh NQ[MQ + XMINs/2],
δPZ ≥ ħ/2RP 0.113
δX/X δPZ/MQ 0.312
XMIN = 1/3 - 2 δX 0.129
MQ = 0.37 ± 0.03 GeV
XMIN = 0.118 ± 0.008
AN ~ F(PT)[G(XA – XTh) -
G(XB – XTh)];
XTh NQ[2MQ /s + XMIN]
Quark interaction with color flux tube in QCD
В dependence on distance r from tube axes:B = -2αsν r/ρ3 exp(-r2/ρ2) (12) where ν – number of quarks, ρ 1.25RC 2.08 GeV-1, RC