Recent phenix results on p p and h production in polarized pp collisions at rhic at s 200 gev
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Recent PHENIX results on p + , p - and h production in polarized pp collisions at RHIC at  s=200 GeV. Frank Ellinghaus University of Colorado (for the PHENIX Collaboration) DIS 2008 April 7-11, London, UK. Spin Sum Rule: The latest…. DSSV, arXiv: 0804.0422

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Frank Ellinghaus University of Colorado (for the PHENIX Collaboration) DIS 2008

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Recent phenix results on p p and h production in polarized pp collisions at rhic at s 200 gev

Recent PHENIX results on p+, p- and h production in polarized pp collisions at RHIC at s=200 GeV

Frank Ellinghaus

University of Colorado

(for the PHENIX Collaboration)

DIS 2008

April 7-11, London, UK


Spin sum rule the latest

Spin Sum Rule: The latest…

DSSV, arXiv: 0804.0422

First “global” (DIS+SIDIS+pp) analysis!

HERMES, arXiv: 0802.2499

DG small in measured range.

Gluon orbital momentum?

Contribution at small or large x?

Gluons carry half the momentum.

Do they carry half the spin?

PHENIX p0 (large gg contribution) does not constrain negative gluon scenarios

very well -> charged pions, direct photons

Frank Ellinghaus, University of Colorado


Enhanced sensitivity to d g and d s

: enhanced sensitivity to DG and Ds?

  • DIS -> Ds small and negative

  • SIDIS HERMES (PRL 92:012005,2004) -> Ds zero or small and positive for x>0.03

  • Latest HERMES result (arXiv:0803.2993) -> Ds zero or small and positive for x>0.03

  • DSSV uses latest FFs from DSS, both fits include the HERMES SIDIS Data

  • -> node at about 0.02

  • DNS also included (HERMES) SIDIS, but has less flexible func. form and

  • uses (quite different) FFs from KKP and Kretzer

Size of Ds important for total quark spin contribution DS

Frank Ellinghaus, University of Colorado


Phenix detector

PHENIX Detector

Frank Ellinghaus, University of Colorado


The phenix detector for spin physics

The PHENIX Detector for Spin Physics

Central Detector:

  • g/p0/h detection

    • Electromagnetic Calorimeter:

      PbSc + PbGl, h < |0.35|, f = 2 x 90

  • p+/p-

    • Drift Chamber

    • Ring Imaging Cherenkov Detector

      Muon Arms:

  • J/y

    • Muon ID/Muon Tracker (m+m-)

  • p0

    • Electromagnetic Calorimeter (MPC)

      Global Detectors:

  • Relative Luminosity

    • Beam-Beam Counter (BBC)

    • Zero-Degree Calorimeter (ZDC)

  • Local Polarimetry -ZDC

Frank Ellinghaus, University of Colorado


Phenix longitudinally polarized pp runs

PHENIX longitudinally polarized pp Runs

Frank Ellinghaus, University of Colorado


H reconstruction via gg decay

h reconstruction via gg decay

  • Energy asymmetry cut: E1-E2 / E1+E2 < 0.7

  • pT > 2 GeV

  • |zvertex| < 30 cm

  • Fit:Gauss+Pol3

2<pT<3 GeV

Frank Ellinghaus, University of Colorado


Invariant cross section

Invariant cross section

L = integrated Luminosity, based on Vernier scan using the BBC

BR= Branching ratio: h 2 photons = 0.3943 ± 0.0026

fAcc = acceptance function from MC (includes smearing)

effTrig (Minimum Bias data) = Trigger efficiency of MB trigger

effTrig (high pT triggered data) = (Trigger effi. MB) x (Trigger effi. high pT

trigger)

effrec = Correct for h loss due to photon conversion (~6% in PBSC,

~8% in PbGl) x loss due to cut on shower shape (~4%)

N = number of reconstructed h

Frank Ellinghaus, University of Colorado


F acc from monte carlo

facc from Monte Carlo

Acceptance and smearing correction from MC

(also accounts for dead regions in EmCal, minimum cuts on photon energies,…)

data

MC

Up to 10% acceptance in PbSc for h at high pT

pT

Frank Ellinghaus, University of Colorado


Photon mb trigger efficiency

Photon/MB Trigger Efficiency

Minimum Bias (MB) trigger efficiency about 80 %

Photon trigger efficiency roughly stable from 4 GeV on (high pT photon trigger threshold is set to 1.4 GeV)

Frank Ellinghaus, University of Colorado


H cross section

h cross section

  • Run 6 h cross section analysis in progress, goes up to 20 GeV!

  • No h fragmentation functions (FFs) in the literature!

  • Enables extraction of FFs from e+e- data and this (large range in pT) pp

  • result ( gluon FFs).

  • Extraction uses method/code from DSS (de Florian, Sassot, Stratmann,

  • PRD75, 2007) ->

Frank Ellinghaus, University of Colorado


H ffs data

h FFs - Data

Frank Ellinghaus, University of Colorado


H ffs comparison

h FFs - Comparison

Describes e+e- data very well over a large range in energies.

preliminary

Will include low-energy high-precision

(prelim.) BABAR data and PHENIX RUN 6 cross

section (25 data points out to 20 GeV) soon.

Hope for HERMES SIDIS data……

Frank Ellinghaus, University of Colorado


H cross section @ 200 gev

PHENIX

Run-05 Preliminary

200 GeV

h Cross section @ 200 GeV

NLO pQCD calculation (m = pT) by M. Stratmann

(uses this h FF, so more a self-consistency check)

  • subprocess fraction needed for

    extraction of DG

Frank Ellinghaus, University of Colorado


H p 0

h / p0

  • has (slightly) enhanced sensitivity

    to gg (when compared to p0) as

    expected

  • Enhanced gg contribution leads to

  • larger asymmetries than for p0

  • sizeable differences in the asymmetry

  • only for max/min scenarios

  • With DG small in currently measured

  • region the difference between p0

  • and h asymmetries is small compared

  • to the current stat. error.

Frank Ellinghaus, University of Colorado


Access to d s

Access to Ds?

Up to 10% contribution from strange quarks….

(Caution: Potentially large uncertainty on s-quark FF due to absence of SIDIS data!)

Frank Ellinghaus, University of Colorado


Inclusive h asymmetries in pp h x

2 < pT < 3 GeV/c

3 < pT < 4 GeV/c

4 < pT < 5 GeV/c

5 < pT < 6 GeV/c

Mgg (MeV)

Mgg (MeV)

Mgg (MeV)

Mgg (MeV)

Inclusive h Asymmetries in pp -> h X

Relative luminosity R using beam-beam counters

Frank Ellinghaus, University of Colorado


Access to d g add the pieces

Measure

Access to DG: Add the pieces…

Access to polarized gluon distribution function via double helicity asymmetry in inclusive polarized pp scattering:

subprocess asym+frac (FFs)

from DIS

Max and min scenarios excluded by h.

Frank Ellinghaus, University of Colorado


Cross section pqcd applicability

Cross section - pQCD applicability

RUN5 200 GeV -- p0

  • p0: pQCD seems at work, with still

  • sizeable scale uncertainties for

  • pT<5 GeV

  • Charged pion cross section so far only

  • extracted from MB triggered data set;

  • PID with TOF

  • ->low pT only

  • Also charge separated cross sections

  • extracted by PHENIX

  • “high” pT triggered (EmCal+RICH) data set;

  • charged pions begin firing the RICH at

  • pT~4.7 GeV,

  • cross section extraction in progress …

PRD76:051106,2007

Frank Ellinghaus, University of Colorado


P p p 0 and the sign of d g

Fraction of pion production

p+, p –, p0 and the sign of DG

Especially in the region where qg scattering is dominant (pT > 5 GeV),

the increasing contribution of d quarks (Dd<0) leads to:

“Model independent” conclusion

possible once enough data is

available.

Frank Ellinghaus, University of Colorado


Comparison to model calculations

Comparison to model calculations

  • Charge separated FFs (DSS, PRD75, 2007) available using SIDIS data (HERMES

  • preliminary); Calculations by W. Vogelsang

  • New Run 6 (2006) result in agreement with Run 5 (2005)

  • More data needed-> Projection for Run 9 (2009) w/o maybe additional higher pT point

Frank Ellinghaus, University of Colorado


Direct photons at s 200 gev

q

g

q

Direct Photons at s=200 GeV

Dominated by qg Compton:

-> small unc. from FFs

-> better access to sign of DG (Dq times DG)

Run-5

Theoretically clean “Golden Channel” is luminosity hungry…

Frank Ellinghaus, University of Colorado


Summary

Summary

  • Charged pion and h data are getting ready to be included in (the next round of) global QCD fits, thanks to new/improved FFs….some more data needed too.

Frank Ellinghaus, University of Colorado


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