Forward Spectrometer Upgrade LOI pp, pA and AA physics

Richard Seto

BNL – EC/DC upgrades meeting

May 5, 2005

General considerations We are now assessing [s?QGP or NOT?] Suppose we got it?

Do we understand it? What is it? How is it made?

Unexpected importance of: Particle ID is surprisingly important even at high pt Forward (backward) rapidities different than central

system is not Bjorken Question : Why not a 4 detector?

Old answer- HI physics is NOT like particle physics – Its more like using a thermometer to measure the temperature (sample the momentum distribution) in a beaker of water

New fact – its like like having several beakers with different conditions

PHENIX

=0.7 [ =.35] electrons (momentum)

Vector mesons charged particles

PID hadrons photons High rate triggers jets (to be added) detached vertex (to be

added)

=3 [ = (1-2.5)] muons(momentum)

vector mesons charged particles (to be

added) ? ? ? ? detached vertex (to be

added)

NCC 0

NCC (+electrons)

Muon Trigger

NCC

0.1 1

0.1

En

erg

y

Den

sity

(G

eV

/fm

3)

10Time (fm)

10

100

I. dAu What is the Initial State of a Relativistic Heavy Ion Collision? A CGC?

Property of initial state

x

Q (GeV)

1

10-1

10-3

10-2

10-4

CGCPurely classical – tree level only

CQFQuantum evolution via anomalous dimension

1 10 100

Qs

QCD

Y~0

Y~4

Y~2

RdA

Rises w/ Npart

Cronin Shadowing:

Higher twist

RdA ~1 (pQCD) Rises w/ Nbin (Nbin)

No Cronin

RdA <1 Falls with Npart

No Cronin Shadowing:

Leading twist

Regions of a nucleus

pQCDCGC boundaryQS

2 =QS(y=0) 2 ey

~0.3

CQF boundaryQS

2 =QS(y=0) 4

high pt suppression !

Where does the high pt suppression come form? Initial State (property of

cold nucleus) Final state (QGP) dA

same effect at >2 =0

RAA

pT (GeV/c) p

T(GeV/c)

RAA

RdA

RdA

conclusion:final state - QGP

conclusion:initial state –cold nucleus

Physics is different in the at >2 ! (new physics to explore)

RCP

M. Liu QM04M. Liu QM04PHENIX prelimPHENIX prelim

x

Q (GeV)

1

10-1

10-3

10-2

10-4

CGC

CQF

1 10 100

QCD

Y~0

Y~4

Y~2

Regions of a nucleus

pQCDCGC boundaryQS

2 =QS(y=0) 2 ey

~0.3

CQF boundaryQS

2 =QS(y=0) 4

PHENIX

BRAHMS

HA

RD

PR

OB

ES

HA

RD

PR

OB

ES

BU

LK

BU

LK

e,

e,

*

?

How do you experimentally see saturation?

Look at Gluon Structure Functions at low-x

Ask Dima, Al, Jamal etc to calculate pA (in order of preference?)

* , ee Direct photons Open Charm J/ production Evolution of quark structure

functions with Q2 – use Drell- Yan as a probe ?

X ~ 1 to 10-4 (evolution) Q2 ~ 1 (saturation) to 50 (pQCD) Functions of

Y= 0 to 4, pT=0 to 10 GeV Centrality

Map out previous diagram

Measuring (gluon) structure functions in the era of NLO and NNLO

LO (leading order) Factorization PDF(x,Q2)pQCD_LO(x, Q2)

Theorists turn out stuff in x, Q2

LO diagram – easy connection between x, Q2 and experimental variables (pT, …)

NLO (next to leading order) Factorization still OK, but use NLO pQCD Connection to x, Q2 messed up

Solution: theorists turn out stuff in terms of experimental variables

Steps (CTEQ)

Choose experimental data sets (get the ones that give the best constraints)

Select factorization scheme, consistent choice of factorization scale etc

Choose the parametric form of the parton distributions and then evolve distributions to any other value of

Find experimentally measured quantities Calculate 2; iterate.

BUT

Don’t we loose information in doing this? Solution– get new observables

Werner – intrinsic KT

Note for some things – heavy quark production –e.g. CGC does not need to put in “KT”, but it comes out of the calculation (same with NLO)

Experiments need to characterize events

as completely as possible

e.g. kT i.e. one needs in direct photons, a measure of the jet energy and directionnote: even for direct photons in the central spectrometer – a measurement of the jet is necessary for the complete characterization of the event, Indeed a jet in the forward region will favor lower x2 for photons in the central arm

Other Stuff

Nuclear Structure (quark level) hadron production in nuclei Multiparton correlations in nucleons (3D-picture) Measurement of three quark component of the

nucleon wave function. Color fluctuations in nucleons: global effects & x-

dependent effects

II AA collisions – Quarkonia C

(Sean Kelly)

state J/ c

' (1s) b

(2s) b' (3s)

Mass [GeV} 3.096 3.415 3.686 9.46 9.859 10.023 10.232 10.355B.E. [GeV] 0.64 0.2 0.05 1.1 0.67 0.54 0.31 0.2

Td/Tc --- 0.74 0.15 --- --- 0.93 0.83 0.74

Onium system as thermometer pT Dependence xF Dependence Study vs system

size and energyBoundBound

precursor color singlet quarkonia

PCM & clust. hadronization

NFD

NFD & hadronic TM

PCM & hadronic TM

CYM & LGT

string & hadronic TM

pre-resonance absorbtion

pre-equilibrum effects

color screening, thermal production

break up by co-moving hadrons

cc J/

quarkonia local timemedium local time

Quarkonia local time gets dilated as a function of pt. This make the ratios of directly produced quarkonia a probe of the plasma lifetime

Time Zones

tau=.1 fm

If we see suppression…

Is it just the cold nucleus? dA

acc and resolution

GeVGeV

Important to keep resolution of muon spectrometer!

Other Stuff to consider in AA

triggering on upsilon for RHIC 2 Photon- high pt particle correlations with

central spectrometer RAA Flow e- for heavy flavor physics vector mesons – to ee p+K ~charged – 0

….

2 track resolution ?

Coverage100x100

QQ22

Log(xLog(x22))

direct photondirect photon

0.5 pb0.5 pb-1 -1 pAu pAu (run 12)(run 12)

log(xlog(x22) )

QQ22=0.1x1 GeV=0.1x1 GeV22

1000 1000 event/binevent/bin

5005001001002020

Requirements

~1-3 Muons

high rate/ triggerable keep good momentum resolution

Calorimeter large acceptance (i.e. can measure jets) can handle high occupancy reasonable emc energy resolution 2 track resolution ~ 2-4 mm reasonable position resolution ability to live close to the beampipe (i.e. can kill

backgrounds – timing? triggerable