071026 adscftday horowitz
Post on 03-Jun-2018
232 Views
Preview:
TRANSCRIPT
-
8/11/2019 071026 AdSCFTDay Horowitz
1/14
AdS Strings Intersect with Nuclear Beams at Columbia110/26/07
William Horowitz
Probing AdS/CFT with Heavy Quarks
William HorowitzColumbia University
Frankfurt Institute for Advanced Studies (FIAS)
October 26, 2007
With many thanks to Miklos Gyulassy,Simon Wicks, and Ivan Vitev
arXiv:0706.2336 (LHC predictions)arXiv:0710.0703 (RHIC predictions)
-
8/11/2019 071026 AdSCFTDay Horowitz
2/14
AdS Strings Intersect with Nuclear Beams at Columbia210/26/07
William Horowitz
Introduction
AdS/CFT looks promising, pQCD alsohas its successes
Desire a robust probe that can cleanlyfalsify one or both formalisms:
Try Heavy Quarks!
-
8/11/2019 071026 AdSCFTDay Horowitz
3/14
AdS Strings Intersect with Nuclear Beams at Columbia310/26/07
William Horowitz
Quantitative AdS/CFT with Jets
Langevin model Collisional energy loss for heavy quarks
Restricted to low pT
pQCD vs. AdS/CFT computation of D, the diffusioncoefficient
ASW model Radiative energy loss model for all parton species
pQCD vs. AdS/CFT computation of
Debate over its predicted magnitude
ST drag calculation
Drag coefficient for a massive quark moving through astrongly coupled SYM plasma at uniform T
not yet used to calculate observables: lets do it!
-
8/11/2019 071026 AdSCFTDay Horowitz
4/14
AdS Strings Intersect with Nuclear Beams at Columbia410/26/07
William Horowitz
Use future detectors identification of c and b todistinguish between pQCD, AdS/CFT
RAA ~ (1-(pT))n(pT), where pf = (1-)pi (i.e. = 1-pf/pi) Asymptotic pQCD momentum loss:
String theory drag momentum loss:
Independent of pT and strongly dependent on Mq!
T2
dependence in exponent makes for a very sensitive probe
Expect: pQCD 0 vs. AdSindep of pT!! dRAA(pT)/dpT > 0 => pQCD; dRAA(pT)/dpT < 0 => ST
rad s L2 log(pT/Mq)/pT
Looking for a Robust, Detectable Signal
ST 1 - Exp(- L), = 1/2 T2/2Mq
S. Gubser, Phys.Rev.D74:126005 (2006); C. Herzog et al.JHEP 0607:013,2006
-
8/11/2019 071026 AdSCFTDay Horowitz
5/14
AdS Strings Intersect with Nuclear Beams at Columbia510/26/07
William Horowitz
Model Inputs for LHC Predictions AdS/CFT Drag: nontrivial mapping of QCD to SYM
Obvious: s = SYM = const., TSYM = TQCD D/2T = 3 inspired: s = .05
pQCD/Hydro inspired: s = .3 (D/2T ~ 1)
Alternative: = 5.5, TSYM = TQCD/31/4
Start loss at thermalization time 0; end loss at Tc
WHDG convolved radiative and elastic energy losss = .3
WHDG radiative energy loss (similar to ASW)
= 40, 100 Use realistic, diffuse medium with Bjorken expansion
PHOBOS (dNg/dy = 1750); KLN model of CGC (dNg/dy = 2900)
-
8/11/2019 071026 AdSCFTDay Horowitz
6/14
-
8/11/2019 071026 AdSCFTDay Horowitz
7/14
AdS Strings Intersect with Nuclear Beams at Columbia710/26/07
William Horowitz
An Enhanced Signal
But what about the interplay betweenmass and momentum?
Take ratio of c to b RAA(pT)
pQCD: Mass effects die out with increasing pT
Ratio starts below 1, asymptotically approaches 1.Approach is slower for higher quenching
ST: drag independent of pT, inverselyproportional to mass. Simple analytic approx.of uniform medium gives
RcbpQCD(pT) ~ nbMc/ncMb ~ Mc/Mb ~ .27 Ratio starts below 1; independent of pT
RcbpQCD(pT) 1 -s n(pT) L2 log(Mb/Mc) ( /pT)
-
8/11/2019 071026 AdSCFTDay Horowitz
8/14
AdS Strings Intersect with Nuclear Beams at Columbia810/26/07
William Horowitz
LHC RcAA
(pT)/Rb
AA(p
T) Prediction
Recall the Zoo:
Taking the ratio cancels most normalization differences seen previously pQCD ratio asymptotically approaches 1, and more slowly so for increased
quenching (until quenching saturates)
AdS/CFT ratio is flat and many times smaller than pQCD at only moderate pTWH, M. Gyulassy, nucl-th/0706.2336
WH, M. Gyulassy, nucl-th/0706.2336
-
8/11/2019 071026 AdSCFTDay Horowitz
9/14
-
8/11/2019 071026 AdSCFTDay Horowitz
10/14
AdS Strings Intersect with Nuclear Beams at Columbia1010/26/07
William Horowitz
LHC RcAA(pT)/RbAA(pT) Prediction
(with speed limits)
T(0): (O), corrections unlikely for smaller momenta
Tc: (|), corrections likely for higher momenta
WH, M. Gyulassy, nucl-th/0706.2336
-
8/11/2019 071026 AdSCFTDay Horowitz
11/14
AdS Strings Intersect with Nuclear Beams at Columbia1110/26/07
William Horowitz
Measurement at RHIC Future detector upgrades will allow for identified c
and b quark measurements
y=0
RHIC
LHC
NOT slowly varying No longer expect
pQCD dRAA/dpT > 0
Large n requirescorrections to nave
Rcb ~ Mc/Mb
RHIC production spectrum significantlyharder than LHC
-
8/11/2019 071026 AdSCFTDay Horowitz
12/14
-
8/11/2019 071026 AdSCFTDay Horowitz
13/14
AdS Strings Intersect with Nuclear Beams at Columbia1310/26/07
William Horowitz
RHIC Rcb Ratio
Wider distribution of AdS/CFT curves due to large n:increased sensitivity to input parameters
Advantage of RHIC: lower T => higher AdS speed limits
WH, M. Gyulassy, to be published
pQCD
AdS/CFT
pQCD
AdS/CFT
-
8/11/2019 071026 AdSCFTDay Horowitz
14/14
top related