Future Measurements at RHIC

1
Future Measurements at RHIC
Richard Seto University of CA, Riverside Workshop
on Nuclear Dynamics Jan 23, Nassau, Bahamas
2
Outline (heavy ions only)

• Long Range Plan for Nuclear Physics
• RD for
• RHIC II
• Upgrade Luminosity x 40
• Electron Ion Collider (EIC)

• Where are we?
• What have we measured?
• What have we learned?
• What next?
• What would we like to know?
• The growth of theory and experiment
• What must we measure?
• An era of precision measurements
• How do we do it?
• Detectors requirements (AA,pA,pp)
• Machine requirements
• Priorities

3
What have we measured? Global FeaturesdET/dy
Initial Energy Density
T 150-200 MeV e 0.6-1.8 GeV/fm3
PHENIX Central Au Au yields
High Initial energy density-Favorable for the
formation of a QGP
4
Initial Conditions- Colored Glass Condensate A
new regime of calculable phenomena in QCD?

• QCD - Notoriously hard to calculate
• Regime where QCD simplifies High Gluon Densities
  at low-x
• Gluon Saturation (CGC- glassfrustrated
  gluons)
• gluons 1/x? , violates unitarity at low x
  ?Gluons saturate
• Classical Approx (McLerran, Venogopolan etc)
• Robust calculations in QCD using
  renormalization group methods
• Depends on a single scale
• ?CGC2 (1/?R2)(dNgluon/dy) gluon density
• Reliable non-perturbative calculations of
  experimental observables
• Nucleus amplifies effect
• Testable in the laboratory eA, pA,ep (very
  low-x)
• RHIC initial conditions

Does it work?
5
What have we measured? Global Features
Equilibration Chemical/Thermal
Chemical freezout
RHIC(130)
Thermal Freezout
?B
Ratio (model)
Model assuming Chemical Equilibration describes
yields Pretty well - ?s 1
6
What have we measured? Global FeaturesElliptic
Flow

• Hydrodynamical model (Kolb et al)
• Rapid thermalization ?0 0.6 fm/c
• ?20 GeV/fm3

Very strong elliptic flow Early thermalization
7
What have we measured? ProbesEnergy Loss from
p0, charged hadrons
High Pt spectra
Calculation of X.N. Wang includes a particular
shadowing parameterization for the structure
functions and kT broadening (Cronin).
8
Jet Fragmentation?
proton/antiproton contribution above pT gt 2 GeV
dominates charged spectra !

• Jetlike
• pTSpectra
• HardNbin
• Pwr law
• Jet frag
• (No flow)

• Thermal
• MT Spectra
• SoftNpart
• Exponential
• Hydro
• (Flow)

Transition?
PID at high PT necessary upgrade
9
What have we learned?
An Amazing Start

• We have made rapid progress on the global
  features of the system
• Initial energy density is high favorable for
  the formation of a QGP
• Saturation approach seems to work!
• ?s, b dependence OK
• Initial or final state effect?
• Need pA data
• Matter appears thermalized
• Tf does not grow with ?s
• ?r grows with ?s
• ? Same phase boundary, but pressure increases
  with ?s
• Strong early pressure build up rapid
  thermalization
• Large pT are at early times- but loose energy
• ? system is strongly interacting it is not a
  free streaming parton system (a Liquid?)
• Probes of the system are just beginning
• Indications of Jet quenching
• Need to see transition from hydro (thermalized
  system) to high pT partons
• I.e. plot switches from mT to pT
• Lepton measurements beginning

10
What Next?

• 2003 2006
• RHIC x4 increase in Luminosity ?
• STAR adds leptonic (electron) signatures
• PHENIX does leptons,photons
• Brahms Coverage to ?4
• Steady Luminosity AuAu runs
• Light Ions runs
• Energy changes
• Baseline pp, dA runs!!

• 2001/2002 (now complete)
• Machine Au Au
• reached design L 2x1026 _at_200 for short
  periods
• detectors need more steady running (phenix10
  of desired triggers)
• Au-Au
• Hadronic signatures, high pT
• STAR event by event studies, ?, resonances
• PHENIX
• Leptons begin (barely)
• Crude pp comparison run

• 2006-?
• Detectors
• Major upgrades
• Machine
• RHIC II (x10-40 in Luminosity)
• Electron-Ion Colider

11
Questions (from the LRP)

• In relativistic heavy-ion collisions, how do the
  created systems evolve? Does the matter approach
  thermal equilibrium? What are the initial
  temperatures achieved?
• Can signatures of the deconfinement phase
  transition be located as the hot matter produced
  in relativistic heavy-ion collisions cools? What
  is the origin of confinement?
• What are the properties of the QCD vacuum and
  what are its connections to the masses of the
  hadrons? What is the origin of chiral symmetry
  breaking?
• What are the properties of matter at the highest
  energy densities? Is the basic idea that this is
  best described using fundamental quarks and
  gluons correct?

12
LRP questions What should we measure?

• What would we like to measure?
• Low mass VM in lepton channel vs energy density
• Critical phenomena
• Quark and gluon energy loss
• Reaction plane
• J/?, ?
• Open charm
• Thermal
• Photons
• Dileptons
• low-x phenomena
• Strange/ anti-baryons, pT spectra
• HBT
• Flow
• Temp/Size/Time profile of the system

• The QCD vacuum
• Mass?
• Chiral Symmetry?
• Transition T
• Confinement?
• Signatures?
• Transition T?
• Properties of matter at high energy density?
  Quarks and gluons correct?
• Understanding the system Created in Relativistic
  Heavy Ion collisions

13
What do we need to do to make the measurement?

• What additional tools do we need?
• Varying energy,species, pp,pA,dA
• Low mass dileptons need dalitz rejection
• Low pt photons
• Very Low pT particles
• Redundancy in lepton signatures
• High rate
• more Luminosity
• High bandwidth
• Good triggering
• Very accurate Vertexing
• Large coverage
• Event by event capability
• High pT PID
• Forward detectors

• What would we like to measure?
• Low mass VM in lepton channel vs energy density
• Critical phenomena
• Quark and gluon energy loss
• Reaction plane
• J/?, ?
• Open charm
• Thermal
• Photons
• Dileptons
• low-x phenomena
• Strange/ anti-baryons, pT spectra
• HBT
• Flow
• Temp/Size/Time profile of the system

14
Pause A new era of Precision?

• Theory Experiment Understanding
• Theoretical Calculations in regions probed by
  experiment
• Experiments in regions calculable by theory
• We (RHI experimentalists) think classically
  our QGP (or hadronic gas) is
  little balls buzzing around in an expanding
  balloon
• In the world of electrons we wouldnt have
• Conductors/Insulators/Semi-conductors.
• Like us to start thinking as quantum mechanics
• Masses? Confinement?
• New era of Precision
• Precision Calculations
• Precision Measurements
• Precision Detectors
• High Luminosity
• AA, pA (dA), pp, eA

The Measurements ? (examples)
15
Example Understanding the right Degrees of
Freedom

• properties of hadrons at high T or ?B
• Assumptions of
• Brown-Rho scaling quark DOF
• hadron masses scale as the quark condensate
• Rapp-Wambach hadronic DOF
• Rescattering and cross sections
• Duality? hadronic ? quark DOF?
• To actually prove this is not possible at the
  moment.
• Theorists will depend on experiment to help
  define the right degrees of freedom to use
• Calculation
• Right now, brute force the lattice
• If we find the right DOF -Understanding of
• transition chiral symmetry
• Transition confinement

• Superconductor Condensed matter
• DOF
• Electrons?
• Phonons?
• Really Cooper pairs
• Calculation-Theorists guessed the right DOF
• QCD matter
• DOF
• Quarks
• Hadrons?
• Something in between?

16
?Precision measurements (examples ?exp
requirements)Probing the vacuum

• QCD
• Spontaneous symmetry breaking (I.e. chiral) of
  the quark condensate at low Temperature generates
  hadron masses
• Light Vector mesons decays to leptons are ideal
  probes (?,?,?) of the hot vacuum created in a RHI
  collision
• Short lifetime few fm/c
• Decay inside the medium

• Lamb Shift in QED

• Lamb Shift
• Shifting of atomic levels due to mass shift of
  the electron due to vacuum fluctuations
• One of the most accurately calculated and
  measured quantities in physics
• Can we do the same?

17
Experimental Knobs

• Signal should be enhanced at low pT

• Signal should increase with centrality

Mee
signal
Mee
18
Dalitz background?

• Problem background from dalitz decays and
  conversions
• Simulation for 109 Central events
• Central events ptlt0.2 GeV (red) compared to
• high pt peripheral renormalized (black)
• Critically important to see vacuum values to
  prove mass resolution is good I.e. you want to
  see a peak Good momentum resolution
• NEED Dalitz rejection via electron ID in a field
  free region.

No datitz rejection
??ee-
19
?Precision Measurements Tagged Jet quenching ?
Detector requirments

• Direct g-tagged events EgEjet
• Compare AA to pp
• Need to measure pT spectrum of particles opposite
  high ET ?
• ? or ?0 ?
• Need to do this vs
• Species/Energy to find energy loss
• How big?
• Proportional to mean free path?
• Gluon/quark difference
• PT
• Reaction Plane

• Large back to back coverage
• EMCAL and tracking
• high pt pid would be good

20
Tomography? (penetrating probes)

• Do as a function of position
• I.e. many bins of centrality, pt, y, reaction
  plane
• E.g
• Jet energy loss
• Mass shift
• Other? (J/? Suppresssion/Charm/)
• Requires
• Very High statistics
• E.g. 10 bin in pt, 5 bins in y,5 bins in
  centrality, 8 bins in reaction plane
• 400 points per centrality 2000 points
• Good geometry measurements
• Reaction plane/centrality event by event
• Ability to invert data

21
?Precision Measurements Onium
Suppression ? Detector requirments

• RHIC add ? family to mix
• Onium system as thermometer
• pT Dependence
• x1,2,F Dependence
• Study vs system size and energy

• SPS Au-Au 0.2-3.5 GeV/fm3
• Statistics on ? was marginal !!

• Need High Rate
• Large acceptance
• Also critical to measure open charm
• VERTEX DETECTION

• RHIC Rates (no suppression)
• J/? Au-Au 0.4 x 106/yr
• ??? 1000 events 30 weeks

22
pA - a critical part of the RHIC program
(2003-2005?)

• pA is critical as baseline for all QGP signature
  for RHI program
• pA-testing ground for QCD
• E.g. low-x parton distributions 2x10-4 (E.g.
  gluon saturation)
• hard diffractive processes
• E.g. parton structure of pomerons/mesons
• collider large acceptance ? large kinematic
  reach

• Improving the situation
• Measure jet associated w/ DY, ?, J/?, etc to get
  x1 , x2 , Q2
• Very tough. Associated current jet is often at
  small angles and must be disentangled from the
  fragmentation jet which heads down the beampipe.
• Improve muon acceptance with a very forward
  detector located in the tunnel. x210-4 for
  ?gt1?
• Large acceptance photon detector in the forward
  region
• Forward tagging via roman pots
• Tagging of nuclear fragments get a handle on
  Ncollisions

? FNAL E866
? MMS
? MMN
? MMSMMN
? Central
x2
1
10-1
10-3
10-4
X2 coverage via drell-yan 100x100 GeV2 pAu
23
Detector upgrades (Money is no object!)

• Tracking
• Good momentum resolution - low mass states/high
  mass states
• Perhaps very low pt
• Large back to back coverage EMCAL and tracking
• High rate capacity
• Tag of detached vertex Dalitz rejection
• PID
• high Pt hadrons
• Leptons (mu/e,dalitz)
• Dalitz rejection
• Good geometry measurements
• pA stuff
• forward muon detector located in the tunnel
  x210-4 for ?gt1?
• Large acceptance photon detector in the forward
  region
• Forward tagging via roman pots
• Tagging of nuclear fragments get a handle on
  Ncollisions
• DAQ
• High Rate
• High BW to tape (balance between acceptance and
  event count)

24
What about luminosity?

• Probes to set the scale
• J/? family, ? family, jets (u,d,c,b,gluon), jet
  ? Of these ?, and high pT jet? (ET gt 15 GeV)
  are the lowest cross sections
• jet?(ET gt 15 GeV) d?/dy/dpT(y0) 5x10-4
  ?b/GeV
• ? (d?/dy)BR 8.6x10-5 ?b
• Look at rates for this
• Study processes 10-4 ?b 1000 events in 30
  weeks
• Detector capabilities
• Large acceptance
• High rate (triggeringdaq band width)
• Require 5000 ? events (5 bins of centrality 3
  measurement more if in pT bins)
• 150 weeks at blue book, 40 weeks at 4xbluebook
• Too much if we want to do various
  species/energies in a reasonable amount of time
• 4 weeks at 40x Bluebook acceptable.
• pA and pp, high luminosity is also required for
• DY 35 weeks for 1000 events at bluebook, M5GeV
• 1 week/1000 events at 40x bluebook

How much?

• x40

25
Priorities (my list)

• Running Time! (Make sure we get this)
• Redundant results are important
• The fact that there are 2 or more detectors
  measuring similar things is a strong feature of
  the program, not a problem
• Major Detector Upgrades (R and D request the
  funding)
• Dalitz rejection
• High ptPID
• Charm (Good vertex detection)
• Extend di-electron capabilities to other
  detectors for redundancy
• Extend Jet detection capabilities to other
  detectors- pp
• For pA
• Forward detectors
• Major Luminosity upgrade (x10 electron cooling)
• For Onium states, ?-jet , DY ..
• May entail major upgrades to detectors
• large acceptance (2?)
• high rate (DAQtriggers)

26
A summary Philosophy

• RHIC provides us with a powerful QCD laboratory
• AA, pA (dA), pp, eA
• Theory Experiment Understanding
• Theoretical Calculations in regions probed by
  experiment
• Experiments in regions calculable by theory
• New era of Precision
• Precision Calculations
• Precision Measurements
• Precision Detectors
• High Luminosity
• Continuing suite of experiments at RHIC/RHIC
  II/eRHIC

27
(No Transcript)
28
What have we measured? ProbesSingle Electron
Spectra
Background subtracted electron spectra
One must account for contributions p0, h
Dalitz g conversions Remaining signal is then
from charm and bottom thermal production
new physics
Charm (pythia)
Now Real Data !
Lepton probes beginning!
29
?/? region

• The ? is complicated since it sits on the ?
  -nevertheless it should be broadened.
• Even if there is no QGP, Rapp predicts a strong
  enhancement of the ?. (which in itself would be
  interesting to see remember the ?clock?)
• A problem with this calculation is that
  correlated charm pairs are not yet in, since the
  line shape of the ? is rather broad. Charm, in
  many scenarios, is also expected to be enhanced

Low pt central
High pt peripheral
Charm- low pt central
Charm-high pt peripheral

• We should be able to identify this if the
  enhancement is as strong as predicted.
• But is it a hot qgp or a cold hadron gas?