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
Dec 28, 2015
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 (AN)
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 FPDE
X STRIP Y STRIP
Eto
wer
YX
Prototype calorimeter located 750 cm (zvert) east of STAR interaction region
Typical single event:
PRL 92 (2004) 171801
6
Forward Production
• Measured large- cross sections consistent with pQCD calculations
• Large transverse single-spin effects observed for s = 200 GeV pp collisions
STAR collaborationPRL 92, 171801 (2004)
7
The STAR Forward Detector
Shower Maximum DetectorHorizontal and Vertical PlanesEach made of 48 strips of plastic scintillator with a wavelength shifting optical fiber through the center of eachMultianode PMTs
Pre-Shower Detector7 vertical lead-glass crystals with PMT+base.
Lead Glass Calorimeter7x7 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 SectionsSTAR Forward p+p Cross Sections
C~5 / B~6
PRL 97 (2006) 152302 D.A. Morozov, hep-ex/0512011
• 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 xF production from:
● q + g q + g (22) + X
● q + g q + g + g (23) + X
g+g andq+g q+g+g
q+g
Soft processes
PYTHIA: a guide to the physicsForward Inclusive Cross-Section: Subprocesses involved:
q
gg
q g
STAR FPD
xF
hep-ex/0403012
10
Run-3 Results from FPDdAu/pp comparisons
PRL 97 (2006) 152302
• 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 Resultsp+p+X analyzing power
PRL 101, 222001 (2008)
Theory (blue): M. Boglione, U. D’Alesio, F. Murgia, PRD 77 (2008) 051502
Theory (red): C. Kouvaris, J. Qiu, W. Vogelsang, F. Yuan, PRD 74 (2006) 114013
• AN(xF) consistent with Sivers function from semi-inclusive DIS (arXiv:0906.3918)
• AN(pT) does not decrease like (pT)-1, as expected by theory
1Brookhaven National Laboratory2University of California- Berkeley3Pennsylvania State University4IHEP, Protvino5Stony Brook University6Texas A&M University7Utrecht, the Netherlands
8Zagreb University
STAR Forward Meson SpectrometerF.Bieser2, L.Bland1, E. Braidot7, R.Brown1, H.Crawford2, A.Derevshchikov4, J.Drachenberg6, J.Engelage2, L.Eun3, M.Evans3, D.Fein3, C.Gagliardi6, A. Gordon1, S.Hepplemann3, E.Judd2, V.Kravtsov4, J. Langdon5, Yu.Matulenko4, A.Meschanin4, C.Miller5, N. Mineav4, A. Mischke7, D.Morozov4, M.Ng2, L.Nogach4, S.Nurushev4, A.Ogawa1, H. Okada1, J. Palmatier3, T.Peitzmann7, S. Perez5, C.Perkins2, M.Planinic8, N.Poljak8, G.Rakness1,3, J. Tatarowicz3, A.Vasiliev4, N.Zachariou5
These people built the Forward Meson Spectrometer (FMS) and/or its components
13
Three Highlighted Objectives In STAR Forward Meson Spectrometer Proposal
[hep-ex/0502040]
1. A d(p)+Aud(p)+Au+X+X measurement of the parton model gluon density distributions xg(x) in gold gold nucleinuclei for 0.001< 0.001< xx <0.1 <0.1. For 0.01<x<0.1, this measurement tests the universality of the gluon distribution.
2. Characterization of correlated pion cross sections as a function of Q2 (pT
2) to search for the onset of gluon saturation effects associated with macroscopic gluon fields. macroscopic gluon fields. (again d-Au)(again d-Au)
3. Measurements with transversely polarized transversely polarized protonsprotons that are expected to resolve the origin resolve the origin of the large transverse spin asymmetriesof the large transverse spin asymmetries in reactions for forward forward production. production. (polarized (polarized pp)pp)
DOE milestone
14
Guzey, Strikman and Vogelsang Guzey, Strikman and Vogelsang Phys. Lett. B603 (2004) 173Phys. Lett. B603 (2004) 173
PYTHIA Simulation 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 xgluon
• provide sensitivity to higher pT for forward reduce 23 (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 ElementsLead Glass From FNAL E831
804 cells of 5.8cm5.8cm60cmSchott F2 lead glass
Loaded On a Rental Truck for Trip To BNL
See talk by A. Gordon
17
FMS High VoltageXP2972 (from E864) + Nanometrics CW bases powered by I2C controlled DAC (L. Eun)
FEU84 (from FNAL-E704 / IHEP) + PSU CW base (L. Eun)
XP2202 + 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:0901.2828
Nikola Poljak – SPIN08
• Azimuthal dependence as expected• AN comparable to prior
measurements
x
y
P
22
Negative xF
J. Drachenberg– SPIN08 arXiv:0901.2763Akio Ogawa – CIPANP 09
Positive xF
RHIC Run 8 with East FPD/FMSpT Dependence
Indication of Positive AN persists up to pT ~5 GeVNeeds more transverse spin running
Negative xF consistent with zero
23
First Look at “Jet-like” Events in the FMSEvent 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” pT > 1 GeV/c ; xF > 0.2• 2 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:0901.2828)
24
•Comparison to dAu •Spin-1 meson AN
High xF Vector MesonsRHIC Run 8 with FMS
Background only MCRun8 FMS dataFit is gaussian + P3
μ=0.784±0.008 GeV σ=0.087±0.009 GeV Scale=1339±135 Events
3 photon events to look for0BR
•PT(triplet)>2.5 GeV/c •E(triplet)>30 GeV•PT(photon cluster)>1.5 GeV/c •PT(π0)>1 GeV/c
Significant (10) 0 signal seen in the data.
A Gordon– Moriond09 (arXiv:0906.2332)
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 6.222 + full GEANT simulations– 9.2 nb-1 Integrated Luminosity
• Full simulation models Mpair data very well
• Data : – Plot includes < 1% of full data set
C.Perkins, QM09 (arXiv:0907.4396)
26
Fit with Gaussian + Offset
Gaussian Fit Parameters:– μ = 3.080 ± 0.020 GeV/c2
– σ = 0.082 ± 0.026 GeV/c2
– χ2/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– Zγγ < 0.7– Isolation Radius:
Reconstructed 2-cluster invariant mass / (~ 6 pb-1 Sampled Luminosity)
– 0.4
– pT_cluster > 1.0 GeV/c
C.Perkins, QM09 (arXiv:0907.4396)
• high-xF 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:0907.3473)
Unc
orre
cted
Coi
ncid
ence
P
roba
bilit
y (r
adia
n-1)
p+p+h±+X, s=200 GeV
requirements:
pT,>2.5 GeV/c
2.8<<3.8
h± requirements:
1.5<pT,h<pT,
h<0.9
• clear back-to-back peak observed, as expected for partonic 22 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
Un
corr
ect
ed C
oin
cid
ence
Pro
bab
ilit
y (r
adia
n-1)
-lead
p+p d+Au
“GSV” Selection “GSV” Selection
2.5 GeV/c<pT(=3)
1.5 GeV/c<pT(||<0.9)<pT
(=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:0907.3473)
30
Azimuthal Correlations (3)
++X
+h±+X
Un
corr
ect
ed C
oin
cid
ence
Pro
bab
ilit
y (r
adia
n-1)
-lead
p+p d+Au
“lower-pT” Selection “GSV” Selection
2.5 GeV/c<pT(=3)
1.5 GeV/c<pT(||<0.9)<pT
(=3)
dAu – pp = 0.09±0.04
“lower-pT” Selection
2.0 GeV/c<pT(=3)
1.0 GeV/c<pT(||<0.9)<pT
(=3)
dAu – pp = 0.19±0.03
Evidence of pT dependent azimuthal broadening of signal
E. Braidot, QM09
E. Braidot (for STAR), Quark Matter 2009 (arXiv:0907.3473)
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 xBj
gluon
Akio Ogawa- CIPANP 09
32
SummaryFMS 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 pT 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 xF-pT 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)