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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
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
….
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