Central Production pppMXp simulations

Kin YipFor STAR CollaborationBrookhaven National LaboratoryPhysics with Tagged Forward Protons at RHICMay 30 - June 4 , 2013, Rehovot/Eilat, IsraelMainly : Elastic pp scattering program at RHIC Results (AN, r5, & ANN/ASS) Central Exclusive Production

STAR

1Sept. 7, 2011Kin YipRHIC-Spin Accelerator Complex June 2, 2013Kin Yip2STARPHENIX AGSLINACBOOSTERPol. Proton SourceSpin Rotators15% SnakeSiberian Snakes200 MeV polarimeterAGS quasi-elastic polarimeterRF DipolesRHIC pC CNI polarimetersRHICabsolute pHpolarimeterSiberianSnakesAGS pC CNI polarimeter5% Snake* ~ 21 m for pp2pp/STAR in 2009Former location of pp2ppJune 2, 2013Kin Yip3Physics with Tagged Forward Protonsp + p p + X + pDouble Pomeron Exchange (DPE)diffractive X= particles, glueballsDiscovery Physics

p + p p + p elastic

Single Diffraction Dissociation (SDD)QCD color singlet exchange: C1(Pomeron), C1azimuthalrapidityThis talk33Sept. 7, 2011Kin Yip

Helicity amplitudes for spin June 2, 2013Kin Yip4Elastic Scattering 4Sept. 7, 2011Kin Yip

AN and Nuclear Coulomb InteractionJune 2, 2013Kin Yip5In the absence of hadronic spin-flip contributions, AN is exactly calculable. [Kopeliovich & Lapidus, Sov. J. Nucl. Phys. 19, 114 (1974).]N.H. Buttimore, et al., Phys. Rev. D 59 (1999) 114010.Our data reach

E704@FNALs = 19.4 GeVPRD48(93)3026pp2pp@RHICs = 200 GeVPLB632(06)167

HJet@RHICPRD79(09)094014no hadronicspin-flipwith hadronicspin-flipHJet@RHICPRD79(09)094014no hadronicspin-flipPrevious AN measurements in the CNI regionJune 2, 2013Kin Yip6no hadronicspin-flip6Sept. 7, 2011Kin Yip

Implementation at RHIC DetectorsJune 2, 2013Kin Yip7

Vertical (-58 m) Horizontal (-55 m)Horizontal (55 m) Vertical (58 m)

IP (STAR)Silicon pitch is ~100 m7Sept. 7, 2011Kin YipThe most significant matrix elements are Leffs , so that approximately :

xD x*

yD y*

Scattered protons have very small transverse momentum and travel with the beam through the accelerator magnets

Roman Pots (RP) get very close to the beam without breaking accelerator vacuum (~ 12 ) Excellent detector efficiencies (plane eff. > 99%) allow us to have clean data.

RP positions have been optimized such that with proper machine optics (parallel-to-point focusing), the positions of the protons at the RPs depend almost exclusively on the scattering angles

Beam transport equations relate measured position at the detector to scattering angles : a11 a13 a14 a21 a22 a23 a24 a31 a32 a33 a41 a42 a43 a44

xxyy

x*x*y*y*

DIP

Roman pots and transportJune 2, 2013Kin Yip88Sept. 7, 2011Kin YipSelection cuts CollinearityJune 2, 2013Kin Yip9

Various data quality and fiducial cuts to select elastic protons and eliminate backgrounds ~21 million events (all spin combinations) One of the most important cuts is collinearity for protons on both sides of IP A typical distribution of x = [x(West) x(East)] and y = [y(West)- y(East)] for a run is shown here.

The width ( 58 rad ) here is consistent with the beam divergence.

The background-to-signal ratio under the Gaussian distributions in 3 is 0.4%.

Calculation of single-spin asymmetry AN June 2, 2013Kin Yip10 Square root formula: dont need external normalization, acceptance asymmetry and luminosity asymmetry cancel out We have all bunch polarization combinations: , , , can build various asymmetrieswhereBeam polarization*: PB= 0.6040.026 and PY= 0.6180.028 (PB+PY) = 1.224 0.038, (PB PY) = 0.016 0.038 = 0.013(PB+PY) and there is an additional global error ~ 4.4% on (PB+PY).

*Averaged for our fills from the official Run09 CNI polarimeter results http://www4.rcf.bnl.gov/~cnipol/pubdocs/Run09Offline/Both beams polarized half of the statistics, but effect ~ (PB+PY)

Opposite relative polarization effect ~ (PBPY) should be close to 0 systematic checkand is the azimuthal angle.

AN fits in 5 binsJune 2, 2013Kin Yip11False AsymmetryPublished: Phys. Lett. B 719 (2013) 6269

Results on AN and r5June 2, 2013Kin Yip121 2 3 no hadronicspin-flipOur fitSTAR

Published: Phys. Lett. B 719 (2013) 6269

r5June 2, 2013Kin Yip13

Phys. Lett. B 719 (2013) 6269

Phys. Lett. B632 (2006) 167- 172

Cannot use square root formula have to rely on normalized counts K+/ = N+/ / L+/where N = # elastic events; L=normalization factor

Double spin effects are seen but very small0.00320 million good elastic events recorded in 5 days of data taking with RPs in 2009 at s=200 GeV and special machine optics *=21 m.Published the most precise measurement of AN at s = 200 GeV (Phys. Lett. B 719 (2013) 6269)

Double-spin asymmetries ANN and ASS and CEP results planned to be submitted for publication in near future.

Planning a Phase II which allows us to study diffractive physics (Central Production, Single Diffraction Dissociation and its spin dependence) and exotic physics etc.

The physics program with tagged forward proton at STAR helps explore physics potential and discovery possibilities at RHIC.

June 2, 2013Kin Yip1919Sept. 7, 2011Kin YipJune 2, 2013Kin Yip20Backup 20Sept. 7, 2011Kin YipRoman Pots (RP) @ STAR in 2009Vertical and Horizontal RP setup for a complete f coverage June 2, 2013Kin Yip21

21Sept. 7, 2011Kin YipJune 2, 2013Kin Yip22Silicon Detector Performance in the 2009 run

Only 5 dead/noisy strips per ~ 14000 active strips (active area limited by acceptance) Overall plane efficiency > 99%. Excellent detector efficiencies allow us to have clean data.

After excluding (3) edge strips and hot/dead stripsData was taken in 5 days ~July 2009 >70 million triggers Elastically triggered ( ~33 million events)Outside sequencer (DAQ) reset time windowValid hit/strip with ADC pedestal_per_channel + 5 A Cluster: 5 valid consecutive hits with ADC sum separated from the pedestal (depending on size)Clusters in A/C and B/D strips are within < 200 m (2 strips)A track on each side (a track is formed by at least a cluster on each Roman Pot)Collinearity (between the scattering angles in the East and West)Timing-vertex cutFiducial cuts and getting rid of hotspots in the RPs nearest to the beam (~tail of the beam) ~21 million events (before considering the spin combinations)June 2, 2013Kin Yip232009 run and main Selection CutsFinalizing the analysis We have focussed our efforts to figure out the best and most accurate transport for the RHIC configuration that we have used during the 2009 run.Cross-checked the transport and the off-axis effects by established software such as MADX and Turtle (to arrive at the same result).Determined (eg.) the signs of angles and magnet strengths related to our experiment with the help of accelerator physicists and dedicated new/old beam experiments.Determining the best way to determine the scattering angle from positions in the RPs (using MC simulation to tell us the accuracies).

We have spent a lot of time in alignment by detector position surveys in the RHIC tunnel and using the (over-)constraints from the elastic data to better align the detector geometry.

A lot of systematic checks have been done. Eg.:June 2, 2013Kin Yip2424Sept. 7, 2011Kin Yip

June 2, 2013Kin Yip25A check to show that we understand the optics of our system:

We compare the slope of the straight line fit of the angle (RP) vs the coordinates(RP) obtained from the data to the slopes of the fits in Turtle simulations when we vary the quad. strength.

For example :

Conservatively assigned an systematic error of 0.5% on magnetic strength 1.4% in -t.P. Pile, et al., in: Proceedings of IPAC12, 2012, p. 1131.One example of systematic checks :

June 2, 2013Kin Yip26