1 Forward Physics Origins of STAR Forward Meson Spectrometer Original physics goals for FMS and overview of implementation Run-8 FMS results, to date Outlook L.C. Bland STAR Review of FMS 1 September 2009

2 STAR Large acceptance near midrapidity Windows to large rapidity

3 Transverse Single-Spin Asymmetries (A N ) Probing for (1) orbital motion within transversely polarized protons; (2) Evidence of transversely polarized quarks in polarized protons.

4 Origins of FMS

5 Run-2 Prototype FPD EE X STRIPY STRIP E tower Y X Prototype calorimeter located 750 cm (z vert ) east of STAR interaction region Typical single event: PRL 92 (2004)

6 Forward   Production Measured large-    cross sections consistent with pQCD calculations Large transverse single-spin effects observed for  s = 200 GeV pp collisions STAR collaboration PRL 92, (2004)

7 The STAR Forward   Detector Shower Maximum Detector Horizontal and Vertical Planes Each made of 48 strips of plastic scintillator with a wavelength shifting optical fiber through the center of each Multianode PMTs Pre-Shower Detector 7 vertical lead-glass crystals with PMT+base. Lead Glass Calorimeter 7x7 matrix of 3.8cm x 3.8cm lead-glass crystals with PMT+base.  0   Rebecca Lamb, RPI undergraduate (BNL/SULI program 1/03 – 5/03) Lead-glass detectors built by IHEP, Protvino group for FNAL E-704 experiment.

8 STAR Forward p+p Cross Sections  C~5 / B~6 PRL 97 (2006) D.A. Morozov, hep-ex/ Forward   cross sections agree with NLO pQCD Cross sections used in DSS global analyses of fragmentation functions PRD 76 (074033) 2007

9 PYTHIA 5.7 prediction agrees well with the inclusive  0 cross section at  3-4 Dominant sources of large x F   production from: ● q + g  q + g (2  2)    + X ● q + g  q + g + g (2  3)    + X g+g and q+g  q+g+g q+g Soft processes PYTHIA: a guide to the physics Forward Inclusive   Cross-Section: Subprocesses involved: q  g g qg  STAR FPD xFxF hep-ex/

10 Run-3 Results from FPD dAu/pp comparisons PRL 97 (2006) d+Au   +X cross section suppressed relative to shadowing expectations d+Au   +h ± correlations are suppressed relative to p+p  Qualitatively consistent with color glass condensate model of gluon saturation

11 Runs 3-6 FPD Results p  +p   +X analyzing power PRL 101, ( 2008 ) Theory (blue): M. Boglione, U. D’Alesio, F. Murgia, PRD 77 (2008) Theory (red): C. Kouvaris, J. Qiu, W. Vogelsang, F. Yuan, PRD 74 (2006) A N (x F ) consistent with Sivers function from semi-inclusive DIS (arXiv: ) A N (p T ) does not decrease like (p T ) -1, as expected by theory

1 Brookhaven National Laboratory 2 University of California- Berkeley 3 Pennsylvania State University 4 IHEP, Protvino 5 Stony Brook University 6 Texas A&M University 7 Utrecht, the Netherlands 8 Zagreb University STAR Forward Meson Spectrometer F.Bieser 2, L.Bland 1, E. Braidot 7, R.Brown 1, H.Crawford 2, A.Derevshchikov 4, J.Drachenberg 6, J.Engelage 2, L.Eun 3, M.Evans 3, D.Fein 3, C.Gagliardi 6, A. Gordon 1, S.Hepplemann 3, E.Judd 2, V.Kravtsov 4, J. Langdon 5, Yu.Matulenko 4, A.Meschanin 4, C.Miller 5, N. Mineav 4, A. Mischke 7, D.Morozov 4, M.Ng 2, L.Nogach 4, S.Nurushev 4, A.Ogawa 1, H. Okada 1, J. Palmatier 3, T.Peitzmann 7, S. Perez 5, C.Perkins 2, M.Planinic 8, N.Poljak 8, G.Rakness 1,3, J. Tatarowicz 3, A.Vasiliev 4, N.Zachariou 5 These people built the Forward Meson Spectrometer (FMS) and/or its components

13 Three Highlighted Objectives In STAR Forward Meson Spectrometer Proposal [hep-ex/ ] d(p)+Au     +X gold nuclei 0.001< x <0.1 1.A d(p)+Au     +X measurement of the parton model gluon density distributions xg ( x ) in gold nuclei for 0.001< x <0.1. For 0.01< x <0.1, this measurement tests the universality of the gluon distribution. macroscopic gluon fields. (again d-Au) 2.Characterization of correlated pion cross sections as a function of Q 2 (p T 2 ) to search for the onset of gluon saturation effects associated with macroscopic gluon fields. (again d-Au) transversely polarized protons resolve the origin of the large transverse spin asymmetries forward   production. (polarized pp) 3.Measurements with transversely polarized protons that are expected to resolve the origin of the large transverse spin asymmetries in reactions for forward   production. (polarized pp)  DOE milestone 

14 Guzey, Strikman and Vogelsang Phys. Lett. B603 (2004) 173 PYTHIA Simulation constrain x value of gluon probed by high- x quark by detection of second hadron serving as jet surrogate. span broad pseudorapidity range (-1<  <+4) for second hadron  span broad range of x gluon provide sensitivity to higher p T for forward    reduce 2  3 (inelastic) parton process contributions thereby reducing uncorrelated background in  correlation.

15 Full azimuth spanned with nearly contiguous electromagnetic calorimetry from -1<  <4  approaching full acceptance detector FPD in far position 50  larger acceptance than run-3 FPD west-south module used for dAu Run-8 Results from STAR Forward Meson Spectrometer (FMS)

16 FMS Detector Elements Lead Glass From FNAL E cells of 5.8cm  5.8cm  60cm Schott F2 lead glass Loaded On a Rental Truck for Trip To BNL See talk by A. Gordon

17 FMS High Voltage XP2972 (from E864) + Nanometrics CW bases powered by I2C controlled DAC (L. Eun) FEU84 (from FNAL-E704 / IHEP) + PSU CW base (L. Eun) XP resistive divider bases, powered by four LRS 1440 HV systems (A. Gordon) 5  Zener diodes per base

18 QT Readout / DSM Trigger Front-end electronics and trigger (C. Perkins)

19 Software, Monitoring and Calibration Overview Event reconstruction from FPD extended to FMS (see L. Nogach and E. Braidot talks) Online monitoring mostly done from trigger data as written by L2 (see talk by A. Ogawa) LED system is the method to monitor FMS gain (see talks by A. Gordon and A. Ogawa) Calibrations are from    reconstruction. Cell-by-cell calibrations partially fed back to HV settings (see talk by L. Nogach)

20 FMS Results

21 Run 8 FMS Inclusive  0 Results Octant subdivision of FMS for inclusive   spin sorting. arXiv: Nikola Poljak – SPIN08 Azimuthal dependence as expected A N comparable to prior measurements x y P

22 Negative x F J. Drachenberg– SPIN08 arXiv: Akio Ogawa – CIPANP 09 Positive x F RHIC Run 8 with East FPD/FMS p T Dependence Indication of Positive A N persists up to p T ~5 GeV Needs more transverse spin running Negative x F consistent with zero

23 First Look at “Jet-like” Events in the FMS Event selection: “Jet shape” in data matches simulation well Reconstructed Mass doesn’t match as well High-Tower Trigger used in Run 8 biases Jets >15 detectors with energy > 0.4GeV in the event (no single pions in the event) cone radius = 0.5 (eta-phi space) “Jet-like” p T > 1 GeV/c ; x F > perimeter fiducial volume cut (small/large cells) “Jet-shape” distribution of energy within jet- like objects in the FMS as a function of distance from the jet axis. Nikola Poljak – SPIN08 (arXiv: )

24 Comparison to dAu Spin-1 meson A N High x F Vector Mesons RHIC Run 8 with FMS Background only MC Run8 FMS data Fit is gaussian + P3 μ=0.784±0.008 GeV σ=0.087±0.009 GeV Scale=1339±135 Events 3 photon events to look for  0   BR  P T (triplet)>2.5 GeV/c E(triplet)>30 GeV P T (photon cluster)>1.5 GeV/c P T (π 0 )>1 GeV/c Significant (10  )  0  signal seen in the data. A Gordon– Moriond09 (arXiv: ) Triple Photons :  0  Next :

25 FMS Minbias Simulations and Association Analysis Fast J/ψ generator + full GEANT simulations Reconstructed quantities match generated quantities quite well Simulation : –PYTHIA full GEANT simulations –9.2 nb -1 Integrated Luminosity Full simulation models M pair data very well Data : –Plot includes < 1% of full data set C.Perkins, QM09 (arXiv: )

26 Fit with Gaussian + Offset Gaussian Fit Parameters: –μ = ± GeV/c 2 –σ = ± GeV/c 2 –χ 2 /d.o.f. = 20.83/26 –Significance from fit 4.5 σ Forward p+p J/ψ – 2-Cluster Analysis Cuts Applied: –E_pair > 60.0 GeV –Z γγ < 0.7 –Isolation Radius: Reconstructed 2-cluster invariant mass / (~ 6 pb -1 Sampled Luminosity) –0.4  –p T _cluster > 1.0 GeV/c C.Perkins, QM09 (arXiv: ) high- x F J/  may have implications for intrinsic charm at large Bjorken- x in proton use to benchmark simulations for future transverse-spin Drell-Yan experiment

27 STAR Detector Large rapidity coverage for electromagnetic calorimetry (-1<  <+4) spanning full azimuth  azimuthal correlations Run-8 was the first run for the Forward Meson Spectrometer (FMS)

28 Azimuthal Correlations with Large  E. Braidot (for STAR), Quark Matter 2009 (arXiv: ) Uncorrected Coincidence Probability (radian -1 ) p+p   +h ± +X,  s=200 GeV   requirements: p T,  >2.5 GeV/c 2.8<   <3.8 h ± requirements: 1.5<p T,h <p T,   h  <0.9 clear back-to-back peak observed, as expected for partonic 2  2 processes fixed and large  trigger, with variable  h  map out Bjorken- x dependence of greatest interest for forward direct-  trigger

29 Azimuthal Correlations (  3)   +   +X   + h ± +X Uncorrected Coincidence Probability (radian -1 )   -  lead p+pp+p d+Au “GSV” Selection 2.5 GeV/c<p T (  =3) 1.5 GeV/c<p T (|  |<0.9) <p T (  =3)  dAu –  pp = 0.09±0.04 “GSV” selection leads to clear back-to-back peak with similar pp/dAu widths as expected by pQCD E. Braidot, QM09 E. Braidot (for STAR), Quark Matter 2009 (arXiv: )

30 Azimuthal Correlations (  3)   +   +X   + h ± +X Uncorrected Coincidence Probability (radian -1 )   -  lead p+pp+p d+Au “lower-p T ” Selection “GSV” Selection 2.5 GeV/c<p T (  =3) 1.5 GeV/c<p T (|  |<0.9) <p T (  =3)  dAu –  pp = 0.09±0.04 “lower-p T ” Selection 2.0 GeV/c<p T (  =3) 1.0 GeV/c<p T (|  |<0.9) <p T (  =3)  dAu –  pp = 0.19±0.03 Evidence of p T dependent azimuthal broadening of signal E. Braidot, QM09 E. Braidot (for STAR), Quark Matter 2009 (arXiv: )

31 Forward  0 – Forward  0 Azimuthal Correlations Possible back-to-back di-jet/di-hadron Sivers measurement Possible near-side hadron correlation for Collins fragmentation function/Interference fragmentation function + Transversity Low-x / gluon saturation study – accessing lowest x Bj gluon Akio Ogawa- CIPANP 09

32 Summary FMS Results to Date Inclusive   analyzing power results consistent with modular FPD results Forward   + mid-rapidity h ± /   azimuthal correlations are observed. The dAu results are consistent with p T dependent azimuthal broadening. Lowest Bjorken-x values are probed when forward   pairs are observed. Clear near-side and away-side peaks are observed for p+p   +   +X Large-rapidity  production observed in p+p collisions at  s=200 GeV Large-rapidity J/  production observed in p+p collisions at  s=200 GeV

33 Run-8 Analysis Outlook Determine normalization for two-particle correlations Extract forward   pair azimuthal correlations from dAu Clustering: towards   +jet or jet+jet Pursue spin dependence of forward   pairs and   

34 Future Plans for FMS Extend p+p     correlations to  ~6, including spin dependence (Run 9, underway) Extend x F -p T map for forward J/  via multi-cluster triggered slow events (Run 9) Forward direct photons and spin dependence (see upgrades talk) Measure analyzing power for forward jets (see upgrades talk) Forward  (see upgrades talk)