Uncertainties in jet event generators due to hadronizaton scheme, Other issues with energy loss on E-by-E hydro, and the extraction of transport coefficients Rainer Fries Texas A&M University RHIC Strategy Meeting Wayne State University, August 24, 2013
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Uncertainties in jet event generators due to hadronizaton scheme, Other issues with energy loss on E-by-E hydro, and the extraction of transport coefficients.
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Uncertainties in jet event generators due to hadronizaton scheme, Other issues with energy loss on E-by-E
hydro, and the extraction of transport coefficients
Rainer FriesTexas A&M University
RHIC Strategy MeetingWayne State University, August 24, 2013
Hadronization, Chemistry and Other Issues
Rainer FriesTexas A&M University
RHIC Strategy MeetingWayne State University, August 24, 2013
RHIC Strategy 2013 3
Hadronization
Rainer Fries
Hadronization: Challenge or Opportunity? HQ sector Quark number scaling
Extraction of Jet/High-PT Physics: JET Hadronization Module
Flavor conversions revisited
RHIC Strategy 2013 4
Hadrons in Heavy Ion Collisions
Rainer Fries
Proton/pion ratio
RAA
“Universal” hadronization in thermalized (low PT) and pure fragmentation (high PT) region.
Intermediate momentum region in heavy ion collisions (2-8 GeV): No kinetic equilibrium; Multi-particle dynamics; No microscopic
description of parton dynamics.
RHIC Strategy 2013 5
Can Hadronization Tell Us About QGP?
Example: Quark Number dependent phenomena
Usual interpretation: quark degrees of freedom were active in the collision.
Rainer Fries
RHIC Strategy 2013 6
Heavy Quark Sector I
Recombination forces heavy quarks to feel the collective flow.
Charm to D-meson coalescence in a recombination model with correct equilibrium limit.
Recombination rate ~ c+light quark elastic scattering rate near Tc.
Rainer Fries
RHIC Strategy 2013 7
Heavy Quark Sector II
Flavor effects in the heavy quark sector: Ds vs D
Changes in chemistry are often hadronization effects.
Rainer Fries
RHIC Strategy 2013 8 Rainer Fries
Baryon/meson ratios: • “jet”: smaller than
inclusive and similar to p+p• ridge: similar to inclusive
inclu
sive A
u+
Au
: M. L
am
on
t (STA
R) S
QM
06
C
u+
Cu
: C. N
attra
ss (STA
R), Q
M2
00
8 A
u+
Au
: J.B. (S
TAR
), WW
ND
07
Jana Bielcikova
C.
Su
are
z (S
TAR
), p
ost
er,
QM
20
08
PH
EN
IX, a
rXiv:0
71
2.3
03
3
pTtrig > 4.0 GeV/c
2.0 < pTassoc
< pTtrig
Au+Au: 2<pTtrig<3 GeV/c,Cu+Cu:3<pT
trig<6 GeV/c
Jana Bielcikova, Hard Probes 2008
Chemistry in Jet and Ridge
RHIC Strategy 2013 9
Recombination in Jet Showers
Rainer Fries
JET goal: jet shower Monte Carlo including medium-modified hadronization
Well-established hadronization models for vacuum shower Monte-Carlo’s Lund string fragmentation Cluster hadronization How to generalize to jets in a medium?
Recombination Challenge: get vacuum fragmentation right. Advantage: medium effects are straight forward to implement; does
well with heavy ion single particle spectra. Need event-by-event formalism; momentum and energy conservation
in each shower are important. Need to include space-time information.
RHIC Strategy 2013 10
String Fragmentation
Here: PYTHIA parton showers, will eventually work with MM showers
Standard PYTHIA Lund string fragmentation:
Rainer Fries
Lund String
String Decay
RHIC Strategy 2013 11
Recombination + Remnant Strings
Here: PYTHIA parton showers, will eventually work with MM showers
Standard PYTHIA Lund string fragmentation:
Our approach:
Rainer Fries
Lund String
Force gluon decay
Recombine
String Decay
Remnant strings
String Decay
RHIC Strategy 2013 12
Recombine Quarks
In absence of space-time information integrate out spatial coordinates in the Wigner functions.
Monte-Carlo implementation of recombination probabilities
Direct recombination produces hard spectra. Allow recombination into resonances with subsequent decay
Mesons: π, ρ, a1, K, K*, and K1 Baryons N, N’, Δ, and Δ’
Reconnect remnant quarks by short strings that fragment.
Rainer Fries
RHIC Strategy 2013 13
Event-By-Event Vacuum Fragmentation
Rainer Fries
Reproduction of vacuum fragmentation compares favorably to PYTHIA string fragmentation.
Sampling thermal partons from a blastwave model (T=170 MeV, <v> = 0.6 (0.65)).
Allow recombination of thermal partons
Rainer Fries
Recombine
Remnant strings
RHIC Strategy 2013 15
Shower-Thermal Recombination
Pions and protons at RHIC. Thermal-thermal added.
Baryon production clearly enhanced by shower-thermal recombination.
Rainer Fries
RHIC Strategy 2013 16
Recover Baryon Enhancement
Proton/pion ratio is enhanced by shower-thermal recombination.
Rainer Fries
RHIC Strategy 2013 17
Lessons So Far?
Hadronization effects in jets: too early to tell the full story
Extrapolating from heavy quarks: jet-thermal recombination adds a layer of diffusion and makes “hard” hadrons feel collective flow. Broadening? Larger v2?
Rainer Fries
RHIC Strategy 2013 18 Rainer Fries
Example 1: excess production of particles which are rare in the medium and rare in the probe sample
Example: photons Need enough yield to outshine other sources of Nrare.
Example 2: chemical equilibration of a rare probe particle
Example: strangeness at RHIC Coupling of jets (not equilibrated) to the equilibrated
medium should drive jets towards chemical equilibrium. Quark-gluon conversion proton/pion ratio