formation and decay of resonances
DESCRIPTION
Formation and decay of resonances. Christina Markert University of Texas at Austin. Motivation Formation time Resonance Correlation Summary and Future Plans. Resonance response to medium. Chiral symmetry restoration Mass and width of resonances - PowerPoint PPT PresentationTRANSCRIPT
Formation and decay of resonances
Motivation
Formation time
Resonance Correlation
Summary and Future Plans
Motivation
Formation time
Resonance Correlation
Summary and Future Plans
Christina MarkertUniversity of Texas at Austin
Christina Markert 125th WWND Big Sky Montana 1-8 Feb 2009
Resonance response to medium
Temperature
Quark Gluon Plasma
Hadron Gas
T Freeze
Shuryak QM04
Chiral symmetry restoration Mass and width of resonances ( e.g. leptonic vs hadronic decay, chiral partners and a1)
Hadronic time evolution From hadronization (chemical freeze-out) to kinetic freeze-out.
Baryochemical potential
part
on
s
Tc
hadro
ns
Christina Markert 225th WWND Big Sky Montana 1-8 Feb 2009
Medium modified resonance (signatures)
A fundamental symmetry of QCD is chiral symmetry. Chiral symmetry is broken by large dynamical mass inconfinement deconfinement leads to partial restoration.Lattice QCD shows that deconfinement and chiral symmetry restoration (CSR) happens at the same temperature
Chiral symmetry Restored
Christina Markert 325th WWND Big Sky Montana 1-8 Feb 2009
Chiral symmetry restoration signal ?
Christina Markert 425th WWND Big Sky Montana 1-8 Feb 2009
NA60
Mediumunmodified
Mediummodified
Width broadening of rho meson
In dimuon spectrum
5
Leptonic decay vs hadronic decay
(1020) yield from leptonic decay looks higher than from hadronic decay
What happened to the mass and the
width?
Effective mass drops: hadronic decay closes up. Increase of BR ratio
)(
)/(
KKBR
eeBR
e+e-
K+K-
25th WWND Big Sky Montana 1-8 Feb 2009Christina Markert
What is the contribution of decay from regenerated resonancesfrom the later hadronic phase ?
6
The general idea: resonances from jets
(CM, R. Bellwied, I.Vitev, Phys.Lett.B669:92-97,2008)
We want early produced resonances and decay in chirally restored medium resonances from jets
Is it possible to have hadron production prior to hadronization, i.e. can there be a mixed phase of degrees of freedom (partons/hadrons) ?
If these hadrons are resonances, can they also decay within the partonic phase or the dense hadronic phase and thus be medium modified ?
partonicmedium
partonicmedium
hadrons/resonances
hadrons/resonances
Resonance formation in heavy ion reactions
1.) Most resonances (u,d,s) are formed when partonic matter transitions back into hadronic matter
sensitive to phase transition properties i.e. chiral symmetry restoration.
2.) Formation of resonances in hadronic matter due to regeneration
3.) Resonances created from a jet within the QGP phase (mixed dof Phase) potentially survive in partonic matter
(QGP)
2.)
Preequili-brium
QGP MixedPhase
3.)
1.)
Hadron gas
temperature
TcTi TkinTchem
Christina Markert 725th WWND Big Sky Montana 1-8 Feb 2009
Mixed dof
Chiral symmetry restored
8
The concept of formation time In string fragmentation as well as general QM considerations
(e.g. Heisenberg’s uncertainty principle) the formation time of a hadron is given by:
A detailed calculation in light cone variables shows a modification due to short formation length for high z hadrons (z1)
o ~ 1 fm/c : proper formation time in hadrons rest frameE : energy of hadronm: mass of hadron E/m = high energy particles are is produced laterheavy mass particles are produced earlier
large z (=ph / pq) = Resonance is leading particle in jet shortens formation time
CM, R. Bellwied, I. Vitev Phys.Lett.B669:92-97,2008.
Formation of hadronic resonances (from jets)
CM, R. Bellwied, I. Vitev Phys.Lett.B669:92-97,2008.
Heavier particles of same momentum formed earlierHigh momentum particles formed later
Christina Markert 925th WWND Big Sky Montana 1-8 Feb 2009
for at RHIC
10
Comparing resonance formation time to QGP lifetime
What is the proper 0 ? (QGP start time)
0 requires thermalization which is an open issue at RHIC and LHC. General approach 0 ~ 1/<pT>
(<pT> RHIC = 450 MeV/c, <pT>LHC = 850 MeV/c) Leads to 0(RHIC)=0.44 fm/c and 0(LHC)=0.23 fm/c
What is the proper QGP lifetime ?
Upper limit based on longitudinal Bjorken expansion QGP = 0 (T0/Tc)3 with
T0(0,RHIC)= 435 MeV and T0(0, LHC)= 713 MeV, Tc = 180 MeV QGP (RHIC) = 6.2 fm/c , QGP (LHC) = 14 fm/c RHIC result slightly higher than data driven partonic lifetime
estimate based on HBT and resonances (QGP (RHIC) ~ 5 fm/c)
Formation Time of Resonances
At LHC the momentum range of resonances decaying inside QGP is extended to higher momentum due to longer
QGP lifetime
RHIC
LHC
(1020): RHIC pT= [3-10] GeV LHC pT=[2-20] GeVChristina Markert 1125th WWND Big Sky Montana 1-8 Feb 2009
12
Lifetime of hadronic resonances
Problem: if we want to measure medium modification of a hadronic resonances through the partonic medium the resonance does not only have to be formed but it also needs to decay in the partonic or the dense hadronic medium.
short lived resonances
But too short a lifetime makes reconstruction difficult (broad states):
Resonances are medium modified short lifetime (e.g. Holt & Haglin, J. Phys. G31 (2005))
modified K*, *, *, are good candidates
Dynamic problem: The resonance formation time will change with mass and momentum.
13
Triggered resonance quadrant correlation analysis
side 1
side 2
near
away
Low pt High pt
near side
No medium or late hadronic medium
No medium (reference data)
away side
Late hadronic medium
Partonic or early hadronic medium (depend on formation time) CSR ?
side 1&2
Thermal hadonic medium
Thermal hadronic medium
near side1 away side2
hadron-resonance correlation
Hadron – (1020) correlation in Cu+CuHadron trigger pT > 3 GeV (2.5M) (1020) asso pT =1-2 GeV
Not corrected for v2
First bin in delta phi
STAR preliminary
STAR preliminary
No evidence for mass shifts andwidth broadenings on the away-side
Most (1020) are from thermal mediumNeed higher pT resonances
Width:6.0±0.7 MeV
Width:7.2±0.9 MeV
M(K+ K-) GeV/c2
M(K+ K-) GeV/c2
Christina Markert 1425th WWND Big Sky Montana 1-8 Feb 2009
HQ2008
Time of Flight detector upgrade at STAR
• Full installation completed in next years (now 65%)• PID at higher momentum • Electron hadron separation
Improves reconstruction of hadronic
and leptonic decay channels:
K* K+(2.5), p*p (11)
ee
Christina Markert 1525th WWND Big Sky Montana 1-8 Feb 2009
Resonances at the LHC
Higher initial temperature Tc: Larger Partonic lifetime. What is the hadronic lifetime ? hadronic decay of resonances
Larger cross section of hard scattering processes
Resonance Program requires:
1.) Good particle identification capability ALICE detector PID: TOF, TPC, TRD, EMCAL 2.) And jet reconstruction capability: EMCAL + fast trigger 10-100 enhancement of jets
Christina Markert 1625th WWND Big Sky Montana 1-8 Feb 2009
K* and at the LHC (ALICE)
Christina Markert 1725th WWND Big Sky Montana 1-8 Feb 2009
Pt jet = 50-60 GeV K*
Francesco Blanco (Houston/Catania)
Jet PT = 50-60 GeVK* TPC acceptance (||<0.9)
Jet PT= 50-60 GeV(1020) TPC acceptance (||<0.9)
Summary
• High momentum resonances from jets could be used as a tool to trigger on early produced resonances and test chiral symmetry restoration
• New detector upgrades at RHIC, and LHC experiments, will help to study higher pT resonances in more detail to study chiral symmetry restoration.
(Also investigate jet triggered leptonic decays)
• High momentum resonances from jets could be used as a tool to trigger on early produced resonances and test chiral symmetry restoration
• New detector upgrades at RHIC, and LHC experiments, will help to study higher pT resonances in more detail to study chiral symmetry restoration.
(Also investigate jet triggered leptonic decays)
Christina Markert 1825th WWND Big Sky Montana 1-8 Feb 2009