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.

Lessons learnt: Resonances important. Event-by-event calculation important.

[K. Han, C.M. Ko, R.J.F., arxiv:1209.1141]

100 GeV light quark jets in e++e-

RHIC Strategy 2013 14

Adding Medium Partons

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

L

N

NN

dt

dN

jet

excess rare,jet

rare

1

gssg e.g.%50

for RHIC GeV 10 @ %5

mediumce

jetjet

du

sw

du

sw

jet photon

g s

Conversions

[RJF, Müller, Srivastava] [Srivastava, Gale, RJF][Zakharov], ….. [Zhang, Vitev][Renk]

[W. Liu, RJF, PRC 77 (2008)] [W. Liu, RJF, PRC 78 (2008)]

RHIC Strategy 2013 19

Conclusions

Chemistry: Need identified hadrons up to 8-10 GeV with good statistics.

Diffusion: out-of-cone energy/momentum in jet measurements near-side correlations of hadrons

Rainer Fries