# Presentation: 738590

## R2D:New physics concepts for the RHIC-II phase

- R2D:New physics concepts for the RHIC-II phase

- Rene Bellwied
- Wayne State University

**Workshop on RHIC-II physics**
**Brookhaven National Laboratory, Nov.19****th****-20****th****, 2004**

## Expression of Interest -A Comprehensive New Detector at RHIC II

- Expression of Interest -A Comprehensive New Detector at RHIC II

- P. Steinberg, T. Ullrich (Brookhaven National Laboratory)
- M. Calderon (Indiana University)
- J. Rak (Iowa State University)
- S. Margetis (Kent State University)
- M.A. Lisa, D. Magestro (Ohio State University)
- R. Lacey (State University of New York, Stony Brook)
- G. Paic (UNAM Mexico)
- T. Nayak (VECC Calcutta)
- R. Bellwied, C. Pruneau, A. Rose, S. Voloshin (Wayne State University)
- and
- H. Caines, A. Chikanian, E. Finch, J.W. Harris, M.A.C. Lamont, C. Markert,
- J. Sandweiss, N. Smirnov (Yale University)
- & RHIC-II workshop ,Yale, April 16/17, 2004

## The Physics Pillars of R2D

- What are the detailed properties of the sQGP and what are the degrees of freedom at high densities ?
- What is the mechanism of  hadronization and is chiral symmetry restored in the deconfined medium ?
- Is there another state (CGC) of matter at low x, what are its features, and how does it evolve into the QGP ?
- What is the structure and dynamics inside the proton (parton spin, L)  and what do we learn from parity violation and polarization measurements ?

## The Measurement Pillars of R2D

- Particle Identified Jet measurements
- Measurement-jets & flavor tagged jets
- Detailed onium measurements
- Forward (low x) physics
- Bulk observables in 4
- High rate spin measurements

## Evolution of a strongly interacting system 

- Measurements:
- 	Initial conditions
- 		( HBT, low-x physics)
- 	Composition above Tc
- 		 (partons, di-quarks, pre-hadrons ?)
- 	Parton density
- 		(jet tomography, flavor,
- 		intra-, inter-jet correlations)
- 	Deconfinement Tc
- 		(Quarkonium melting)

## What are the initial conditions ? 

- Color Glass Condensate (CGC):
- gluon saturation at low Q2. Measure
- Mid – forward rapidity correlations (hep-ph/0403271)
- Direct photons at forward rapidities
-   HBT (coherence of sea-quark source?)
- Drell-Yan in forward region (hep-ph/040321)
- RpA, RAA of heavy mesons in forward direction (hep-ph/0310358)
- requires tracking, calorimetry and PID over large -range.

##          Bulk dynamics in 4

-          Bulk dynamics in 4

- change (, pT)
-  vary (B ,T)
-  vary x

-      limiting fragmentation

-           forward HBT

- Need tracking
- & PID forward

## In and out of a sQGP 

- What are the degrees of freedom above TC ?
- Is chiral symmetry restored above TC ?
- How does hadronization and spontaneous breaking of chiral symmetry (SBCS) occur ?

## The sQGP degrees of freedom and chiral symmetry restoration

- C.Greiner (Jamaica 04): multi-gluon interactions (e.g.strong 2 to 3)
- Recombination models: constituent quark (dressed up valence quarks)
- C.Greiner (SQM04): high mass resonances near Tc (Hagedorn states)
- E.Shuryak (QM04): colored and colorless bound states above Tc
- Measurements:
**High mass resonance shifts due to partonic bound states (Shuryak)**
**Resonances to prove SBCS**
**Is off mass shell resonance (e.g. shifting or broadening in mass) visible in chiral partner pairs (******** and a****1****) or (******** and ********) ?**
**Resonances in jets**
**Is the leading particle resonance different from the bulk matter resonances (off shell vs on shell, same side vs away side, leading vs. next-to-leading)**

## Hadronization and fragmentation via particle identified jet physics

- pT

- pQCD

- Hydro

- ~ 2 GeV/c

- ~ 6 GeV/c

- Soft

- Medium modifiedfragmentation (jet quenching)

- 0

- pT independence of pbar/p ratio.
- p/  and /K ratio increases with pT to > 1 at pT ~ 3-4 GeV/c in central collisions.
- Suppression factors of p,  different to that of , K0s in the intermediate pT region.

- Parton recombinationandcoalescence

- Fragmentation

- ~ 30 GeV/c ?

## 0 in pp: well described by NLO

- 0 in pp: well described by NLO

- Ingredients (via KKP or Kretzer)
- pQCD
- Parton distribution functions
- Fragmentation functions

**p+p->********0**** + X**

- hep-ex/0305013 S.S. Adler et al.

## Strange particles in pp

**Specific NLO calculation describes K****0**** reasonably well, but is off for ******
**W.Vogelsang:********maybe********is too heavy, problems with heavy particles**
**B.Jaffe (PAC meeting):**** maybe we need to look at fragmentation again**
**RHIC-II will be the premier pp machine in the next decade **
**because of its detector capabilities**

## Do we understand fragmentationand its modification ?

- statistical approach based on measured inclusive
- cross sections of baryons in e+e- annihilation:
-        alternate: de Florian et al., (1998)
-                      or J.J.Yang (2001,2002)

- Modification according to
- Gyulassy et al. (nucl-th/0302077)
- Quite generic (universal) but attributable to radiative rather than collisional energy loss

- z

- z

## Different partons lose different amounts of energy

**Examples:**
**1.) dead cone effect for ****heavy quarks****:**
**For heavy quarks in the vacuum and **
**in the medium the radiation at small **
**angles is suppressed (Dokshitzer & **
**Kharzeev, PLB 519 (2001) 199)**** **

**2.) ****gluon**** vs. quark energy loss:**
**Gluons should lose more energy and have higher particle multiplicities due to the color factor effect.**

## Gluon jet selections at RHIC-II

- 1.) Large rapidity interval correlations
-       (Mueller-Navelet Jets)
- 2.) Three jet events (?)
- 3.) PT-dependence of -jets (?)

## The goal of particle identified fragmentation in the medium

- 1.) we need to understand fragmentation (hadronization) in pp collisions
- 2.) use the medium modified fragmentation functions in AA collisions
- 3.) Different flavor contributions to D(z) at different z lose different z in the opaque medium.

## -charged hadron correlations in pp and AA

**Quark vs. gluon jet ?, baryon-meson effect ?**
**flavor conservation ?**
**No significant difference for different trigger **
**particle species at intermediate trigger pt.**
**But we are statistics limited, **
**we need ********Anti-********K to higher pt**
**Anticipated R2D rates:**
**50,000 ******** pairs > 4 GeV/c , 5,000 pp pairs > 10 GeV/c **

- STAR preliminary

## Asymmetry might develop as a function of trigger pt (increased ‘jettiness’)

- STAR
- preliminary

## Requirements for a complete jet program  

- Broadening in  and pT  in pp (+jet) and AA

-  Full coverage in tracking and pid and calorimetry

- R2D rates per RHIC year: 40 GeV di-jets: 120k
- NChwith pt>5 GeV/c in -jets with E = 20 GeV : 19,000

- Need hadronic calorimetry in order to apply isolation cuts for ’s

- Glueck et al., PRL 73, 388

## Onium physics – the complete program 

- Melting of quarkonium states (Deconfinement TC)
- Tdiss(’) < Tdiss((3S)) < Tdiss(J/)  Tdiss((2S)) < Tdiss((1S))
- In order to resolve the question of melting of the states and its relevance to the sQGP we need to measure:
- 		the J/ production mechanism (octet vs. singlet model)
- 		the effect of thermal recombination
- 		the effect of nuclear absorption
- 		the effect of co-mover absorption
- 		the feed-down from c
- 		all states

## Why a more complete onium program ?

- In pp:
- understand charm production
- (singlet vs octet model)

- In pA
- nuclear absorption:
- dependent on xF or x2 ?

- In AA:
-  co-mover absorption:
- Realistic cross sections ?

## Requirements for a complete onium program

- Full coverage high resolution forward calorimetry in order to measure not only the J/ but also the c and the Y States

- Full coverage (||< 3) calorimetry and muon absorbers give us up to 1,000,000 c, 10,000 Y(2s) and 10,000 Y(3s) per RHIC year. The J/ alone is not sufficient !

- R2D

## Charm flow by STAR/PHENIX

- STAR data very preliminary

## How can something so heavy flow with the light quarks ? 

- Either lots of interactions of the
- heavy quark with the rest of the
- partonic phase or the hadronic
- phase (thermalization ?)
- What are the degrees of freedom ? :
- dressed up constituent quarks, bare heavy quarks, gluons, colorless bound states (glueballs ?).
- Let’s measure v2 for D (through hadron channels),
- B-mesons (through J/channelsJ

## RHIC-II: the premier pp machine for the next decade

- Attract new (and old) communities:
- RHIC Spin
- High energy hadron physics
- (Fermilab, Jlab, GSI)
- (proton driver at FNAL ?)
- - quark models, lattice gauge tests
- - meson/baryon exotica
- - glueballs, multiquark states
- - diffractive physics, multi-pomeron
- Contacts: M.Albrow, J.Appel (FNAL)
- E. Swanson (Pitt), T. Barnes (ORNL)

- Higher luminosity by varying quad position & superbunches

## Origin of Spin (of Proton)

- Gluons
-  -jet (provides x range) *
- Heavy quarks (D, B) *
- Heavy quarkonia (J/tag)
- Large ET jets (ET ~ 40 - 50 GeV jets)
- Sea-quarks
- Anti-quarks (W production)  *
- Strange quark (Charm-tagged W production)
- Orbital Angular Momentum? Polarization in AA?
- * part of original RHIC Spin program

## RHIC-II: the premier pA machine for the next decade

- Attract new communities:
- (in preparation for EIC)
- eA community (Jlab, DESY)
- CGC theory
- wee partons, CGC
- high parton density QCD
- gluon production, spin structure
- Contacts: A.Deshpande (SUNY)
- R.Milner (MIT), BNL- CGC folks

## Do we need RHIC-II in the LHC era ?

- Is the LHC viewing the sQGP through the distorted lens of the Color Glass Condensate  ? (M. Gyulassy)
- Maybe the QGP degrees of freedom change from RHIC to LHC. Does the sQGP get weaker ? Are we in the sQGP sweet spot ?
**The case needs to be made strongly by the theory community that is interested in RHIC-II.**
- The LHC detectors are not sufficient to characterize the sQGP.

## Requirements according to RHIC II Physics Pillars

**Detailed properties of sQGP**
**Quarkonium: EMC/HCal Resolution, Acceptance, Rates**
**Jets: PID and tracking at high p****T**** over full** acceptance (-jet, jet-jet)

**Mechanisms of hadronization**
**PID at High p****T****, correlations, large ******** acceptance, ********-tagged jets**

**Origin of Spin (of Proton)**
**Large ******** acceptance, jets, ********-jet, high p****T**** identified particles, correlations**

**Low x physics (CGC ******** QGP)**
**High-p****T**** identified particle yields to large ******
**Multi-particle correlations over small & large ******** range**

## Do we need a new RHIC-II detector ?

- Understanding QCD at high density requires hermetic detectors with complete PID, HCal, EMCal, and tracking coverage.
- The upgrades to the existing RHIC detectors do not fulfill the necessary detector requirements.
- The LHC detectors do not cover all the requirements.
- A new device is required in order to harvest the uniqueness of the RHIC-II physics program.