PHYSICS WITH TAGGED FORWARD PROTONS AT RHIC Kin Yip For STAR Collaboration Brookhaven National Lab. Aug. 31, 2009, Tatranská Štrba, Slovakia Mainly : Introductions and Expectations First look at the data (2009 RHIC run)

RHIC-S PIN A CCELERATOR C OMPLEX STAR PHENIX AGS LINAC BOOSTER Pol. Proton Source Spin Rotators 15% Snake Siberian Snakes 200 MeV polarimeter AGS quasi-elastic polarimeter RF Dipoles RHIC pC “CNI” polarimeters RHIC absolute pH polarimeter Siberian Snakes AGS pC “CNI” polarimeter 5% Snake  * ~ 21 m for pp2pp/STAR in 2009 Former location of pp2pp

Relativistic Heavy Ion Collider (RHIC): THE QCD Factory QCD (theory of strong interaction): some of the current and future QCD measurements at RHIC Confinement/phase of QCD - QGP Distribution of spin in the nucleon - Spin sum rule Parton splitting limit - Saturated gluon state (Color Glass Condensate … ) Gluonic degree of freedom in Hadrons – exotica (glueballs … ) Nature of diffractive processes – structure of Pomeron, Odderon … 3

4 PHYSICS WITH TAGGED FORWARD PROTONS AND THE STAR DETECTOR p + p  p + X + p Double Pomeron Exchange (DPE) diffractive X= particles, glueballs Discovery Physics p + p  p + p elastic Single Diffraction Dissociation (SDD) QCD color singlet exchange: C  1, C  1

In the double Pomeron exchange process, each proton “emits” a Pomeron and the two Pomerons interact producing a massive system M X where M X =      gg(glueballs),  c (  b ), qq(jets), H(Higgs boson), The massive system could form resonances. We expect that because of the constraints provided by the double Pomeron interaction, glueballs, hybrids, and other states coupling preferentially to gluons, will be produced with much reduced backgrounds compared to standard hadronic production processes. For each proton vertex one has t four-momentum transfer  p/p M X = invariant mass 5 CENTRAL PRODUCTION IN DPE pp MxMx RHIC

Coupling of the exchange particles to the final state mesons for gluon exchange (small dp T ) and quark exchange (large dp T ) Spin-dependence of the coupling can be studied at RHIC 6 “Large” ~ (≥ O(  QCD ) PLB (1997) Kinematic “filter” (dp T ) for “gg” (F. Close et al./W102) Large dP T q

7 Summary of the Existing Elastic Data ( unpolarized ) RHIC  Highest energy so far: pp: 62 GeV (ISR) p : 1.8 TeV (Tevatron)  RHIC energy range: 50 GeV  s  500 GeV  Elastic measurements: Details on the nature of elastic scattering between the ISR and SPS energies NOT well understood: Unique measurements in wide t-range with polarized beams pp2pp 2003

Can Odderon be identified at RHIC ? Odderon is a counterpart of pomeron (C   1) with C   1: “RHIC is the machine to find it” (E. Leader, Odderon Workshop (2005)) by measuring  (  pp –  p ) ≠ 0 (~3mb) d  /dt pp ≠ d  /dt p Shape of Asymmetries: A NN Centrally produced C  1 particle 8 hep-ph/ M. Islam et al. UA4      diffraction alone hard-scattering alone

J.H. Lee 9 I MPLEMENTATION AT RHIC  D ETECTORS Roman Pots of pp2pp  STAR (existing equipment)  Need detectors (Roman Pots) to measure forward protons: small t (four-momentum transfer),  (  p/p) and M X (invariant mass)  Detector with good acceptance and particle ID (STAR) to measure centrally produced system TPC tracking in |y|<1 with TOF barrel and TPC PID (p/K separation up to~ 1.6 GeV/c)

10 RUN PHASE I ( ) Elastic scattering: 1.100% acceptance for elastic scattering for  |t|  0.022; 2.With 20-40×10 6 elastic events, accurarices:  b=0.31 [cf. ~1.8] (GeV/c)  2,  =0.01,  tot = 1-2 mb; 3.In four t subintervals we shall have 5×10 6 events in each resulting in corresponding errors  A N = [cf.  0.005],  A NN =  A SS =0.003 [cf /0.008]. Important conditions: Need to reach small t and  values to measure small masses of interest  large  *~21m (cf. ~0.7 m), special optics and beam collimation are needed. Alignment very important  use elastic events; Hence a dedicated five day run for pp2pp

t-acceptance of Roman Pots Phase I set-up focuses on low-t (installed) Phase II covers higher-t range 11

Expected reconstructed phase-space including BR per 1M DPE events M x =1-3 GeV/c 2 is kinematically well accessible in pion and kaon decay channels High-Mx reconstruction is limited by PID (  /K separation up to ~ 1.6 GeV/c) Expected Trigger rate for DPE: 80 Hz at L = 1x10 31 cm -2 s -1 To collect 100K K + K - sample, needs only ~200 hr of running time 12 √s=500 GeV Phase II Acceptance & Expected yields in M X Possible as NO special accelerator optics will be required

13 TAGGING FORWARD PROTONS AT RHIC THE PP2PP ELASTIC SCATTERING EXPERIMENTAL SETUP Phys. Lett. B 579 (2004) , Phys. Lett. B 632 (2006) , Phys. Lett. B 647 (2007)

Roman Pots moved to STAR Vertical AND Horizontal RP setup for a complete  coverage 14

Aug. 31, 2009 Kin Yip 15 (cm) Cluster position Y vs X in Roman Pots (strip numbers) Z-Vertex from the opposite PMT’s Online/QA

(ADC’s) of the clusters in silicons Aug. 31, 2009 Kin Yip 16 in the unit of ADC’s Online/QA

17 Collinearity of candidate elastic events Online/QA Mean ~  ~ 0.15 Mean ~  ~ 0.15 (strip numbers)

The Accounting Department … ~33 M events elastic triggers Selected “cleanest events” for later analysis which satisfy the following conditions: Valid hit/strip with ADC  pedestal_per_channel + 5  Cluster (≤5 valid consecutive hits) with total energy  20 Treating 4 opposite roman pot pairs separately,  1 valid opposite pair “golden tracks” (with 1 cluster on each of the 4 planes in each Roman Pot)  ~78% (of elastic triggers) in a typical run Required additional collinear conditions  ~74% (of elastic triggers) Aug. 31, 2009 Kin Yip 18

19 Candidate Central Production Event An STAR event triggered by the PMT’s in the Roman Pots

20 Summary We’ve had a great run - the setup and its integration with STAR worked very well (33M elastic triggers, 700k CP triggers) We will focus now on data analysis: Elastic scattering - spin dependence A NN, A N, A SS, A S,  tot for the spin combinations. Elastic scattering - spin averaged dN/dt => slope b,  tot, , luminosity measurements. Diffraction - Central Production, Single Diffraction Dissociation and its spin dependence.  Hope to have results in near future …. There is more to do to fully explore physics potential and discovery possibilities at RHIC Each proton run at RHIC allows to expand our research

BACKUP SLIDES April 29 DIS09 21 J.H. Lee

ROMAN POTS (PHASE I) Phase I: 8 Roman pots at ±55.5, ±58.5m from the IP Require special beam tune :large  * (21m for √s=200 GeV) for minimal angular divergence Ready to run in 2009: Will be focusing small-t processes (0.002<|t|<0.03 GeV 2 ) April 29 DIS09 22 J.H. Lee

ROMAN POTS (PHASE II) Phase II: 8(12) Roman Pots at ±13 and ±16m Planed to be implemented in Doesn’t require special beam tune: main set-up for central DPE processes requiring wide-t coverage and high-luminosity 2  coverage will be limited due to machine constraint April 29 DIS09 23 J.H. Lee

April 29 DIS09 J.H. Lee 24 R OMAN P OTS USED ( ) FOR PP 2 PP EXPERIMENT AT RHIC to IR Roman Pot (below the beam) Roman Pot (above the beam) pp2pp set-up