Single Spin Asymmetry of Charged Hadron Production by 40 GeV/c polarized protons

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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

Transcript of Single Spin Asymmetry of Charged Hadron Production by 40 GeV/c polarized protons

  • Polarized Proton Beam Line 22 at IHEP

    MH, MV magnets; P1 absorber; K collimator; T target.

    Primary proton beam: 60-70 GeV/c, 1013 ppp, hits Be target T.

    Polarized protons from -decays: P = 39 2 %, 3.5107 ppp,40 GeV/c, p/p = 4.5 %, spill 1.3 s., + admixture 1.5 %, beam polarization was changing each 18 minutes during 30 s.

    V.V. Abramov, FODS-2 Experiment

  • Secondary Target Region & Beam Monitoring

    Q magnetic lens; MV vertical corrector; T1 target; beam cherenkov counter; S scintillation counter; IC ionization chamber; HB beam hodoscope.

    Beam monitoring: Intensity (S, IC); Composition ();Position (IC, HB).Targets: Liquid H2 0.05 int; Carbon, Copper, Lead 0.10 int.

    V.V. Abramov, FODS-2 Experiment

  • FODS-2 Rotating Double Arm SpectrometerT1 Target H Hodoscope cherenkov counterS Trigger counter DC Drift chamberPC Prop. chamber SCOCH Ring imagingcherenkov spectrometer HCAL Hadron calorimeter STEEL Muon detector MAGNET absorbs beam Two arms allowed to cancel some apparatus biases.

    V.V. Abramov, FODS-2 Experiment

  • SCOCH cherenkov Ring Imaging SpectrometerHPM Hodoscopephotomultipliers

    Identification:

    +, , K+, K, p, p

    24 HPMs

    V.V. Abramov, FODS-2 Experiment

  • SCOCH cherenkov Ring Imaging Spectrometer

    Identification range: +, (2-40 GeV/c); K+, K (5-40 GeV/c); p, p (10-40 GeV/c).

    V.V. Abramov, FODS-2 Experiment

  • MeasurementsRegion 1: cm = 105o 0.25 xF 0.05 0.7 pT 3.0 GeV/c

    Region 2: cm = 86o0.15 xF +0.20 0.5 pT 4.0 GeV/c Region 3: cm = 48o+0.05 xF 0.70 0.5 pT 2.5 GeV/c

    V.V. Abramov, FODS-2 Experiment

  • Measurements 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.

    V.V. Abramov, FODS-2 Experiment

  • 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.

    V.V. Abramov, FODS-2 Experiment

  • 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 m 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.

    V.V. Abramov, FODS-2 Experiment

  • Analyzing Power for p + A + X There is no significantA-dependence of AN.

    There is a breakdownin pT-dependence withmaximum near 2.5 GeV/c.

    First + 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.

    V.V. Abramov, FODS-2 Experiment

  • Analyzing Power for p + A X AN 0 for cm 85o.

    First 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.

    V.V. Abramov, FODS-2 Experiment

  • 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 + asymmetry. In both cases valence u-quark contributes to the hadron production.

    V.V. Abramov, FODS-2 Experiment

  • 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.

    V.V. Abramov, FODS-2 Experiment

  • Analyzing Power for p + A p X AN 0 for cm 88o.

    AN oscillates as a function of pT with minimum at 1.3 GeV/c and maximum near 2.2 GeV/c for cm 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.

    V.V. Abramov, FODS-2 Experiment

  • 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.

    V.V. Abramov, FODS-2 Experiment

  • AN for p + A + 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 + data for cm > 90o.

    V.V. Abramov, FODS-2 Experiment

  • AN for p + A 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 data for cm > 90o.

    V.V. Abramov, FODS-2 Experiment

  • 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 cm > 90o.

    V.V. Abramov, FODS-2 Experiment

  • AN scaling for + production at high xFAt high energies and PT scaling is expected:

    AN ~F(PT)[GA(XAX0)-GB(XB X0)]XA = (XR + XF)/2 -u/s;XB = (XR XF)/2 -t/s;X0 = 0.075NQ + 2NQMQ(1+coscm)/sMQ= 0.3 GeV, quark mass. NQ=2 in + XS = XA X0 ;In forward region (cm 0, where it shows a scaling behaviour.

    V.V. Abramov, FODS-2 Experiment

  • AN scaling for production at high xFAN ~F(PT)[GA(XAX0)-GB(XBX0)]X0 = 0.075NQ+2NQMQ(1+coscm)/sXS = 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.

    V.V. Abramov, FODS-2 Experiment

  • AN energy dependence for protonsAN ~F(PT)[GA(XAX0)-GB(XB X0)]

    X0 = 0.075NQ+2NQMQ(1+coscm)/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.

    V.V. Abramov, FODS-2 Experiment

  • SummaryAN was measured for +, , K+, K, p & protons at FODS-2 setup. The mean angle cm 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 & p show near zero AN for pC & pCu collisions as expected due to small sea quarks polarization.Breakdown in pTdependence of analyzing powers for +, 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 cm = 105o is close to zero.Scaling behavior of AN in the forward region & pT > 0.6 GeV/c.

    V.V. Abramov, FODS-2 Experiment

  • xF -dependence of AN for + and production

    V.V. Abramov, FODS-2 Experiment

  • AN energy dependence for protons

    V.V. Abramov, FODS-2 Experiment

  • Dimensional SSA analysis and scaling Scaling for large of s, -t u:AN = AN (PT/PTh, PT/PTQ, MQ/s, xA, xB) (4)

    PT < PTh 1/Rh 0.35 GeV (quarks are not seen inside hadrons)PTh < PT < PTQ (constituent quarks revealed)PT > PTQ 3/RQ 2.7 (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 in c.m.: ETh NQ[MQ + XMINs/2], (7)where NQ number of quarks in ; XMIN minimal momentum fraction carried by constituent quark Q.

    V.V. Abramov, FODS-2 Experiment

  • Energy dependence of hadron C threshold energy (ETh) in c.m.ETh NQ[MQ + XMINs/2], PZ /2RP 0.113

    X/X PZ/MQ 0.312

    XMIN = 1/3 - 2 X 0.129

    MQ = 0.37 0.03 GeV XMIN = 0.118 0.008AN ~ F(PT)[G(XA XTh) - G(XB XTh)];XTh NQ[2MQ /s + XMIN]

    V.V. Abramov, FODS-2 Experiment

  • Quark interaction with color flux tube in QCD dependence on distance r from tube axes:B = -2s r/3 exp(-r2/2) (12) where number of quarks, 1.25RC 2.08 GeV-1, RC-1 0.6 GeV, RC confinement radius.

    Stern-Gerlach force: (Ryskin, 1987)fx = x Bx/x + y By/x (13) fy = x Bx/y + y By/y (14) Longitudinal chromoelectric and circular chromomagnetic fields in the color flux tube. = sggs/2MQ chromomagnetic moment of constituent quark.

    V.V. Abramov, FODS-2 Experiment

  • Polarization effects in color flux tube fieldS ~ lf ~ p ~ PAXA (if formation length is less than S )

    AN ~ Px ~ sin(kS)/a ~ sin(kS)/(g 2) (20)kS ~ XA/MQ ~ AXA(21) G(XA) ~ sin[A(XA - XTh)], (22)where XTh takes into account threshold energy ETh. Quark path length (S) in color flux tube at fixed pTS ~ RT/sin(Lab) ~ p/pT ~PAXA/pT

    V.V. Abramov, FODS-2 Experiment

  • Experimental data and dependence on kinematical variables (A + B C + X) AN and PN dependence:

    AN = F(PT)[G(A, xA) - ()G(B, xB )] (23) G(A, xA) = C(s ) sin[A(xA -