PHYSICS WITH TAGGED FORWARD PROTONS AT RHIC

Kin YipFor STAR Collaboration

Brookhaven National Lab.

Aug. 31, 2009, Tatranská Štrba, Slovakia

Mainly : Introductions and Expectations First look at the data (2009 RHIC run)

RHIC-SPIN ACCELERATOR COMPLEX

STARPHENIX

AGS

LINACBOOSTER

Pol. Proton Source

Spin Rotators

15% Snake

Siberian Snakes

200 MeV polarimeter

AGS quasi-elastic polarimeter

RF Dipoles

RHIC pC “CNI” polarimeters

RHIC

absolute pHpolarimeter

SiberianSnakes

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…

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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: C1, C1

In the double Pomeron exchange process, each proton “emits” a Pomeron and the two Pomerons interact producing a massive system MX

where MX = 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

MX = invariant massඥ𝛏𝟏𝛏𝟐 𝐬

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CENTRAL PRODUCTION IN DPE

p p

MxRHIC

Coupling of the exchange particles to the final state mesons for gluon exchange (small dpT) and quark exchange (large dpT)

Spin-dependence of the coupling can be studied at RHIC

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“Large” ~ (≥ O(QCD

)

PLB 397 339 (1997)

Kinematic “filter” (dpT) for “gg” (F. Close et al./W102)

LargedPT

q

𝒒ഥ

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Summary of the Existing Elastic Data ( unpolarized )

50 500

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

𝐩ഥ

pp2pp2003

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/dtpp ≠ d /dtp

Shape of Asymmetries: ANN

Centrally produced C1 particle 8

hep-ph/0210437 M. Islam et al.

UA4

diffraction alone

hard-scattering alone

J.H. Le

e

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IMPLEMENTATION AT RHIC DETECTORS

Roman Pots of pp2pp STAR (existing equipment)

Need detectors (Roman Pots) to measure forward protons: small t (four-momentum transfer), (p/p) and MX (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)

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RUN 2009 - PHASE I ( )

Elastic scattering:

1. 100% acceptance for elastic scattering for 0.003 |t| 0.022;

2. With 20-40×106 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 5×106 events in each resulting in corresponding errors AN=0.0017 [cf. 0.005],

ANN=ASS=0.003 [cf. 0.017/0.008] .

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

ξ𝒔 = 200 GeV

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 Mx=1-3 GeV/c2 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=1x1031cm-2s-1

To collect 100K K+K- sample, needs only ~200 hr of running time 12

√s=500 GeVPhase II

Acceptance & Expected yields in MX

Possible as NO special accelerator optics will be required

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TAGGING FORWARD PROTONS AT

RHIC THE PP2PP ELASTIC SCATTERING EXPERIMENTAL SETUP

221121 yxyxpp

,,

Phys. Lett. B 579 (2004) 245-250, Phys. Lett. B 632 (2006) 167-172, Phys. Lett. B 647 (2007) 98-103

QuickTime™ and a decompressor

are needed to see this picture.

Roman Pots moved to STAR

Vertical AND Horizontal RP setup for a complete coverage

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Aug. 31, 2009

Kin Y

ip

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(cm)

Cluster position Y vs X in Roman Pots

(strip numbers)

Z-Vertex from the opposite PMT’s

Online/QA

Online/QA

(ADC’s) of the clusters in siliconsA

ug. 31, 2009K

in Yip

16

in the unit of ADC’s

𝒅𝑬𝒅𝒙 Online/QA

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Collinearity of candidate elastic events

Online/QA

Mean ~ -0.12 ~ 0.15

Mean ~ -0.02 ~ 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 Y

ip

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19

Candidate Central Production Event

An STAR event triggered by the PMT’s in the Roman Pots

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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 ANN, AN, ASS, AS, 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 D

IS09

21

J.H. L

ee

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 GeV2)

April 29 D

IS09

22

J.H. L

ee

ROMAN POTS (PHASE II)

Phase II: 8(12) Roman Pots at ±13 and ±16m

Planed to be implemented in 2010-2011

Doesn’t require special beam tune: main set-up for central DPE processes requiring wide-t coverage and high-luminosity

2coverage will be limited due to machine constraint

April 29 D

IS09

23

J.H. L

ee

April 29 D

IS09J.H

. Lee

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ROMAN POTS USED (2002-2003) FOR PP2PP EXPERIMENT AT RHIC

to IR

Roman Pot

(below the beam)

Roman Pot (above the beam)

pp2pp set-up