1. Transverse Spin Physics at ANDYx1 x2
Akio Ogawa
for ANDY collaboration
Transversity2014
Chia, Cagliari
2014 June 12

2. Goal of ANDY Project
Measure the analyzing power for forward Drell-Yan production to test the predicted change in sign from semi-inclusive deep inelastic scattering to DY associated with the Sivers function
GEANT model of proposed ANDY apparatus (run-13) 2

3. AnDY History 2010 May LoI to PAC – Encouraged for full proposal
2011 Feb-April Run11 data taking (partial Ecal)
2011 May Proposal – Endorsed by PAC
2012 April-June Run12 data taking (partial Ecal + Ecal moved out)
2012 April BNL review – time constrain & man power issue
IP2 was committed to Coherent Electron Cooling
We still got very interesting data on Jets from run11 & 12

4. Expectations for Jet AN (Prior to Measurements)
Left
from p+pp+X
“old” Sivers function
“new” Sivers function
s=200 GeV
arXiv:
Right
arXiv:
√s=200 GeV
pjT(GeV)
√s = 500 GeV jets have 2.5x larger pT at the same xF relative to these predictions.
Jets integrate over p+, p-, and p0
“Mirror” AN for p+ and p- should result in cancellations for jet AN

5. Run-11 setup ANDY at IP2 Trigger/DAQ electronics
Beam-beam counter (BBC) for minimum-bias trigger and luminosity measurement (from PHOBOS [NIM A474 (2001) 38])
Zero-degree calorimeter and shower maximum detector for luminosity measurement and local polarimetry (ZDC/ZDC-SMD, not shown)
Hadron calorimeter (HCal) are L/R symmetric modules of 9x12 lead- scintilating fiber cells, (10cm)2x117cm (from AGS-E864 [NIM406(1998)227])
Small ECal - 7x7 matrices of lead glass cells, (4cm)2x40cm (loaned from BigCal at JLab)
Preshower detector - two planes, 2.5 & 10 cm
For run 12, the HCal was made annular
Left/right symmetric HCal
Left/right symmetric
ECal
Left/right symmetric preshower
Trigger/DAQ electronics
Blue-facing BBC
Beryllium vacuum pipe
PMT end view of 10cm x 10cm HCal cell 5

6. Run-12 setup Goal: to establish from measurement
HCal Left/Right modules used in run-11 were modified into annular 20x12 detector with 2x2 hole for the beam pipe
Goal: to establish from measurement
effects from trigger bias on run-11 jets 6

7. HCal Calibration - 0
Relative calibration of HCal cells by cosmic ray muon
Absolute energy scale is set by:
slope matching of energy distributions from minimum-bias data and simulation
2) reconstruction of p0gg from HCal “EM clusters”
Cuts applied to select “electromagmetic” clusters:
(1) 1-tower clusters; (2) Ecl > 1.8 GeV;
(3) Epair > 5 GeV; (4) zpair < 0.5;
(5) |x|>50 cm to avoid ECal shadow
Energy resolution for EM shower
~< 10%/ sqrt(E)
Corrections to HCal calibration for hadron showers are expected to be ~15% from simulations
Cluster pair mass distributions in HCal modules
from minimum-bias run-11 data and simulations
(absolutely normalized) arXiv:
HCal works well as Ecal *IF* no Ecal in front & segmented to smaller cell size

8. HCal - Hadronic Response
Leading cluster to proton (antiproton)
Subleading cluster to p- (p+)
Attribute peak in invariant mass to Lamba (anti-Lambda)
E =1.12 x EEM-calibration – 0.1 GeV
1.15 from GEANT simulation
Include
everything
K0* Only
Simulation
Leading cluster : K- (K+)
Subleading cluster to p- (p+)
Attribute peak in invariant mass to K0*

9. Jet Reconstruction – Anti-kT Jet Finder
Trigger on HCal masked ADC Sum in L/R Modules
Display anti-kT jet clusters satisfying acceptance cuts
Anti-kT Jet Finder Procedure :
Iteratively merge pairs of clusters until clusters cease to satisfy distance criteria
No Seed
Towers can be outside trigger region
Distance Criteria (clusters j,k) :
djk = min(k-2Tj,k-2Tk)(R2jk/R2)
R2jk = (ηj – ηk)2 + (Φj – Φk)2
If djk < k-2Tj then merge clusters j,k
Use cone with radius = 0.7 in η-Φ space but cluster towers can fall outside of cone
Impose acceptance cuts to accept/reject jet:
|ηJ – 3.25| < 0.25
|ΦJ – ΦOff| < 0.50
where ΦOff = 0 for HCL
ΦOff = π for HCR
Energy Cut : Ejet > 30 GeV
Algorithm :
arXiv :
arxiv :
Events look “jetty” / Results with anti-kT algorithm similar to midpoint cone algorithm
14 June 2013

10. Reconstructed Jet Kinematics
Fiducial volume requirements
3<jet<3.5
|jet-off|<0.5, where off=0 for left and  for right.
A strong correlation between jet xF and pT, as shown.
E = 25GeV to >150GeV
pT = 2 to >10GeV
25GeV
100GeV
Color axis=number of events used in jet AN analysis

11. Data/Simulation Comparison
30-50GeV
50-70GeV
70-90GeV
Tower multiplicity
Jet pT
Jet shape
Jet pT and xF are calculated ignoring mass
good agreement between data and simulations above trigger threshold
Jet-triggered data is well described by simulation 11

12. Multiplicity Distributions
Jet-triggered data is generally well described by simulation
Particle multiplicities of forward jets are comparable to what is observed in e+e- at s10 GeV. PRD 56 (1997) 17
Transverse momenta of forward jets at RHIC are similar to those probed in FermiLab fixed target experiments PRL 38 (1977) 1447; PRL 41 (1978) 9; PRL 44 (1980) 514; PRD 31 (1985) 984.
Average ~5.5 hadrons per jet (counting pi0, not photons)

13. Jet Energy Scale - Simulation
arXiv:
Simulations confirm energy scale of jets, by comparison of “tower” jets [with full detector response] to “particle” jets [excluding detector response].
Reconstructed jets are directionally matched to hard-scattered partons as generated by PYTHIA
Correlation between tower jet [from PYTHIA/GEANT] to particle jet [from PYTHIA]. The inset shows the  component of the directional match () between particle jets and a hard-scattered parton, whose direction is defined by parton,parton. There is a 82% match requiring ||,||<0.8

14. Jet Energy Scale - Data
2-jet mass bump attributed to 2b2 gluons
attributed to (1S)3 gluons
attributed to C(1P)2 gluons
Jet energy scale also determined from mass peaks in multi-jet events
Hadronic decays of bottomonium well characterized in e+e- PRD 56 (1997) 17
 production observed through +-g by ATLAS at LHC PRL 108 (2012)

15. Jet Cross Section
Measured forward jet cross sections include point-to-point systematic errors as shown.
PYTHIA [Comp. Phys. Commun. 135 (2001) 238] predate tunings of PYTHIA for LHC.
PYTHIA [JHEP 05 (2006) 026] includes tunings of PYTHIA to Tevatron data for use at the LHC.
NLO pQCD
A.Mukerjee, W.Vogelsang
Phys. Rev. D 86 (2012)
[arXiv: ]
NLO pQCD agree well with our measurement

16. Jet Analyzing Power AN(jet) is small and positive for xF,jet>0
Preliminary results [arXiv: ] reported comparable AN with the mid-point cone algorithm.
Systematic errors do not include scale uncertainty from the beam polarization measurements
AN(jet) is small and positive for xF,jet>0
Compatible with cancellations from pion production: AN(p+)AN(p-)
Compatible with Sivers functions fit to semi-inclusive DIS

17. AN comparison with Theory
From fits to SIDIS Sivers moments Projected for pp forward jet AN
Leonard Gamberg, Zhong-Bo Kang, Alexei Prokudin
Phys. Rev. Lett. 110, (2013)
arXiv:
Twist-3 3 gluon correlation (200GeV)
Y. Koike et al
arXiv:
Divided by 10
M. Anselmino et al
PhysRevD
arXiv:

18. AN for ECal-triggered jet vs Hcal-triggered jet
Run11 data only
cone-jet algorism
ECal triggered jet biases towards EM rich jets
more pi0 like AN
bias extends well beyond the trigger threshold

19. Backgrounds for DY Dijets are the reducible background to DY
Cross sections are efficiency corrected, following similar procedures used for inclusive jet cross section
PYTHIA yield is too small
PYTHIA yield is too large
<kT> best described by PYTHIA 6.425
A hint of D from Ks+
a handle on irreducible open-HF background asymmetry?

20. Conclusions & Outlook
Forward jet cross section was measured – NLO pQCD agrees well
Forward jet AN was measured – Small and positive - Consistent with theory
Forward di-jet cross section was measured - this will help future RHIC
ANDY people are still working towards RHIC in STAR and PHENIX
Some of ANDY equipment are moved to STAR for forward upgrades
"What is dead may never die, but rises again, harder and stronger.”
“A Feast for Crows” by GRRM

21. Backup
14 June 2013

22. Jet Energy Scale - II PYTHIA 6.425 simulation of (1S)3 gluons3 jets
(no backgrounds)

23. Jet Cross Section-I Definition
The jet invariant cross section is:
where
N – number of particles detected
trig – trigger efficiency
det – detection efficiency
Lsamp – sampled luminosity (time integrated), calibrated by vernier scan
<cosh()> - average value of cosh() over the acceptance, y
<pT> - average value of transverse momentum in acceptance
,  - specifies the geometry of the acceptance
E – width in energy of bin considered
This shows an evaluation of the trigger efficiency from PYTHIA/GEANT. Inefficiency results from variation of  for each tower for the extended source for the colliding beams. etrig is checked by extracting cross section from minimum-bias triggers

24. Spin Direction
The analyzing power for forward neutron production [AN(n)] has been measured to be positive [PLB 650 (2007) 325]
AN(n) is measured with zero-degree calorimeters [NIM A 499 (2003) 433], and provides colliding beam experiments with a local polarimeter.
Confirm the spin direction used for jet measurements by measuring AN(n) concurrent with measuring AN(jet).
This fixes the sign of AN(jet).

25. Jet Analyzing Power Definition and Systematics
AN(jet) exploits mirror (left/right) symmetry of apparatus with spin-/spin- of colliding beams, via a cross-ratio…
Systematic errors for AN(jet) are in part computed by varying parameters analogous to manner done for cross section.
Bottom line is that AN(jet) is statistics limited, because of cancellation of systematic errors from symmetry.

26. Transverse Single Spin Asymmetries in p+ p+X
Right
Left
Theory expectation: small AN for collinear pQCD at leading twist [Kane, Pumplin, Repko, PRL 41 (1978) 1689]
AN O(10-4) Theory
Experiment: p+ p- p0
E704
√s=20 GeV
STAR
PRL 101 (2008)
Phys. Lett. B 261 (1991) 201
Phys. Lett. B 264 (1991) 462
AN O(10-1) Measured

27. Two of the Explanations for Large Transverse SSA
Collins mechanism requires transverse quark polarization and spin-dependent fragmentation
Sivers mechanism
requires spin-correlated transverse momentum in the proton (orbital motion). SSA is present for jet, g or g* (DY)
Require experimental separation of Collins and Sivers contributions
Jet（and DY)　have no Collins contributions
14 June 2013

28. Jet Cross Section-II Run Dependence
Multiple systematic checks were made for the cross section. This plot shows two:
In addition, results were obtained from jet-triggered and minimum-bias triggered samples, to check consistency.
Comparison of cross sections from left and right modules
Stability of cross section with time.

29. Jet Cross Section-III Systematic Errors
The stability of the jet cross section was examined as jet-finder (R,Ethr); jet acceptance (d,d); jet energy scale (S) and vertex selection (dzvert) parameters were varied.
Results with jet triggered (open squares) and minimum-bias triggered (open circles) events are shown.
Projections of the resulting cross section on the variation index J result in distributions for each energy bin used to estimate the systematic error for that bin.

30. Spin Sorting Blue single beam Yellow single beam
RHIC has a pattern of polarization directions injected for each fill.
Polarization for colliding beams is established by counting (C) the 9.38 MHz clock, and identifying specific bunch crossings by B=mod(C,120)
Polarization pattern for a fill is communicated from the accelerator to the experiments.
Bunch counter distributions also assess single-beam backgrounds

31. Attractive vs Repulsive Sivers Effects
Unique Prediction of Gauge Theory !
Simple QED
example:
DIS: attractive
Drell-Yan: repulsive
Same in QCD:
DOE performance milestone HP13
As a result:
Transverse Spin Drell-Yan Physics at RHIC (2007)

32. Status of the ANDY Project See http://hena. lbl
A new effort at RHIC to make the first measurement of the analyzing power (AN) for Drell Yan (DY) production at s=500 GeV
2010 – Letter of Intent reviewed by program advisory committee (PAC)
2011 – model apparatus operated in RHIC run 11 / full proposal endorsed by PAC
2012 – ~2.5 pb-1 in RHIC run 12 / time constraint and manpower issues from Brookhaven review

33. Hcal Calibration – Cosmic Ray Muon
Prior to run 11 operation, HCal modules had relative PMT gains set by cosmic-ray muon response.
Triggering enabled verification of scintillating fiber attenuation length in each detector
ADC data from beam-left module with fits to Landau distribution (centroid shown) + exponential background

34. Trigger bias for forward jets
Tower multiplicity for the jet trigger (left) and ECal sum trigger (right) events
30 < Ejet < 50 GeV
50 < Ejet < 70 GeV
70 < Ejet < 90 GeV
HCal trigger threshold ~ 35 GeV
30 < Ejet < 50 GeV
50 < Ejet < 70 GeV
70 < Ejet < 90 GeV
ECal trigger threshold ~ 22 GeV
ECal trigger biases jets, and the bias extends well beyond the trigger threshold
The trigger bias imposed by ECal likely prefers jets that fragment to a hard neutral pion