S' PrattNSCLMSU - PowerPoint PPT Presentation

1 / 20
About This Presentation
Title:

S' PrattNSCLMSU

Description:

Thermal Model HBT. HBT Weight: Use parameters to get. weight: T=190 MeV, l ... Thermal Model Diffusion. Procedure: Generate a pair thermally at h=0, t=t0. ... – PowerPoint PPT presentation

Number of Views:21
Avg rating:3.0/5.0
Slides: 21
Provided by: nscl5
Category:

less

Transcript and Presenter's Notes

Title: S' PrattNSCLMSU


1
Hadronization When and How
Scott Pratt, Michigan State University
  • Is hadronization delayed beyond 1 fm/c timescale?
  • What is the pre-hadronic state? (QGP? quark
    soup? gluonic slush?)
  • Is strangeness produced at hadronization?
  • Are anti-baryons produced at hadronization?

2
Charge is Created at Hadronization
  • Gluonic modes carry entropy, but no charge
  • Coalescence of quarks at sameT should have
    ? quark number doubles
  • Coherent sources (chiral fields, bag energy) can
    produce new charge.

Over half of electric charge, strangeness and
antibaryons should be created at hadronization!
3
Suppose one could identify balancing Charges
Early hadronization ? large dh Delayed
hadronization ? small dh
4
Balance Functions How They Work
For each charge Q, there is one extra balancing
charge Q.
Charges electric, strangeness, baryon number
5
Balance Function Properties
In general, B(P2P1) is 6-d object
P2 can refer to any function of pa and
pb. Simple Example P1 ? anywhere in the
detector P2 ? relative rapidity
6
Balance Function Properties
If chance of finding balancing charge 100,
? normalizes to unity True even when
?Q? ? 0.
  • Normalization reduced for
  • Imperfect Acceptance
  • Loss of Charge through other channels, e.g.,
    p balanced by K-.

7
Balance Function Properties
Relation between Balance Function and Q
Fluctuations S.Jeon and S.P., hep-th (2001).
  • Similar relation between C(y) and F2(D). Wieand
    et al., PLB (89)
  • B(y) more physically transparent.
  • Each pair contributes ONCE and ONLY ONCE.
  • Easier to analyze errors.

8
Balance Function Properties
Statistical Errors
  • Error independent of multiplicity
  • KK, pp, pp have same error
  • number events determined by
  • chance of observing balancing charge.

9
Thermal Model
  • Assume Q Q produced at same point.?Dy?
    determined only by T and m.
  • Proton balance functionnarrower that pions.
  • Thermal model always narrower than string model.

10
Thermal Model HBT
  • HBT Weight
  • Use parameters to getweight T190 MeV, l.7,
    Rinv7 fm
  • Dip at small Dy
  • Applied to non-partners
  • Proportional to dn/dy
  • Does not change norm.
  • No significant changein ??y?
  • Dip similar to that seenby STAR

S.Jeon and S.P., hep-th (2001)
No HBT HBT Coulomb
11
Thermal Model Radial Flow
  • Inclusion of flow requires lower temperature
    but not lower transverse mass
  • Result Narrower B(Dy)
  • Would make more sense to plot as function of Qinv

12
Thermal Model Resonances
  • Resonances may be less important for AA
  • May affect normalization (loss of charge to
    other channels)
  • Can be crudely accounted for by using lower T
  • For more complete treatment, see talk of Sen
    Cheng

13
Thermal Model Diffusion
  • Procedure
  • Generate a pair thermally at h0, tt0.
  • Perform Ncoll collisions randomly in ln t.
  • Between collisions, move particles with
    straight-line trajectories.
  • Rethermalize to local T flow velocity.T(t01
    fm/c) 225 MeVT(tf15 fm/c) 120 MeV
  • For Annihlations, convolute pairs.

Collisions Annihilations magnify difference
between early vs. late creation !
14
Balance Functions Quantitative Expectations
Hadronic Model pp Balance functions 10
BROADER for AA than for pp due to diffusion.
Proton-antiproton balance functions become
broader due to annihilation.
RQMD, provided by Q.H.Zhang.
  • Delayed Hadronization
  • Width determined by Breakup T.
  • pp Balance functions 25 NARROWER for Central
    AA than for pp.

15
What if Balance functions are observed to be
NARROWER for AA than they are for pp?
RQMD-type descriptions are qualitatively
wrong AND
EITHER
  • Late-stage production of charge
  • Anomalously short mean free paths
  • Change in degrees of freedom
  • QGP least exotic explanation

OR
  • would be contrary to common wisdom

16
What if AA balance functions are BROADER?
RQMD, provided by Q.H.Zhang.
  • Gluonic modes did not contribute to entropy
  • No dramatic change in degrees of freedom.
  • Usual strangeness enhancement arguments are
    wrong.
  • J/Y Jet-quenching phenomenology are misguided.

17
Preliminary STAR Results
M. Tonjes, ParkCity, 2001
Identified Pions
More Central Collisions ? Narrower Balance
Functions !!!
18
STAR Summary
QUANTITATIVELY consistent with HIJING ?
Thermal Production in Late Stage
19
STAR, width vs. centrality
All Charges
Identified Pions
As b? 0, data are consistent with 100
delayedproduction with T 110 MeV, v? 0.75
20
Can We Convict the QGP?
  • Analyze pp collisions.
  • Analyze KK- and pp balance functions.
  • Decipher pt dependence.
  • Study as functions of Qbeam, Qout, Qside, Qinv.
  • Quantitatively understand normalization.(Loss of
    partners to other channels, e.g., p balancing
    partner could be K-.)
  • Much can be accomplished with STARs 200 GeV data
  • PHENIX may be able to measure pp balance function
Write a Comment
User Comments (0)
About PowerShow.com