first high p t physics prospects with the photon spectrometer at alice kenta shigaki (hiroshima...
TRANSCRIPT
First High pT Physics Prospects
with the
Photon Spectrometer at ALICE
Kenta Shigaki(Hiroshima University )
for the ALICE Collaboration
3rd Joint Meeting of DNP’s of APS and JPSOctober 14, 2009
Waikoloa, Big Island, Hawaii
+ all PHOS and PWG4 (jet/photon) collaborators
Most Relevant Members
2/12Oct.14, 2009
Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki
Kenta Shigaki Aya Hiei Hisa Torii
LHC/ALICE/PHOS status and schedule high pT neutral mesons in first year of
ALICE– statistics and pT reach
– technical challenges and resolutions first high pT physics prospects
– 0 in Pb+Pb run in 2010– more work in progress
summary and concluding remarks
Presentation Outline
Oct.14, 2009
3/12Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki
collisions in 2009/12; physics awaited in 2010 ALICE under commissioning
– cosmic data taking ongoing– LHC beam (p and Pb) also seen
3(/5) PHOS modules installed; being cooled down
LHC/ALICE/PHOS Status & Schedule
4/12Oct.14, 2009
Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki
September, 2009Pb beam injection oriented
Jet Quenching at LHC
Oct.14, 2009
5/12Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki
higher pT reach + stronger suppression than RHIC– clearer measurement of quark energy loss
e.g. quark flavor/spin dependent suppression?
“day-1” ALICE physics program– enough acceptance with initial 3 PHOS modules
assumptions:– 10 TeV p+p;
5×1028 cm2s1;180 days×10%
– 0 in NLO/CTEQ6M/KKP;particle ratios from PYTHIA
– 3/5 PHOS geom. coverage (~ high pT limit) only
Statistics + pT Reach in 1st p+p Run
Oct.14, 2009
6/12Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki
assumptions:– 3.9 TeV Pb+Pb;
5×1025 cm2s1;30 days×10%;~ 10% central (b < 5 fm)
– NLO pQCD×PYTHIA×N-N binary scaling (1,150 for central Pb+Pb)×suppression (0.1)
– 3/5 PHOS geom. coverage (~ high pT limit) only
Statistics + pT Reach in 1st Pb+Pb Run
Oct.14, 2009
7/12Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki
statistics not really an issue
LHC First Year versus Years at RHIC
8/12Oct.14, 2009
Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki
Technical Experiencesand More
multi-photon decay channels challenging kinematic cut optimization to improve S/B careful combinatorial background
subtraction PHOS: highest resolution ever in RHI
experiments
PHENIX 0Au+Au peripheral (cent
60~92 %)3.5 < pT < 4.5 [GeV/c]
pT() [GeV/c]
S/√
B
(sig
nifi
cance
)
before cut optimization
after cut optimization
PHENIX example 0
Oct.14, 2009
9/12Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki
WA9813 GeV Pb+Pb
nucl-ex/0108006
PHENIX200 GeV Au+Aurun 2
ALICE14 TeV p+p
GEANT simulation
single particle simulation– NLO pQCD×PYTHIA×N-N binary
scaling×suppression– mass reconstruction in ALICE analysis framework
acceptance for multi-photon decays two-cluster resolution (merging effect) photon identification
1 M central Pb+Pb HIJING at 3.9 TeV– locally generated at Hiroshima
“hybrid” approach– multiplicity effects in next steps
embedding study by combining the two
Feasibility Evaluation Ingredients
0
Oct.14, 2009
10/12Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki
better S/B, not necessarily S/(S+B), at higher pT
0 in ~ 10% central Pb+Pb at 3.9 TeV; RAA = 0.1 5×1025 cm-2 s-1, 30 days, 10% uptime
feasible up to >> 10 GeV/c more species (, , K0
s) under study
S/B and S/(S+B)
Oct.14, 2009
11/12Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki
0 peak visible in central Pb+Pb HIJING
consistent S/B in NLO/HIJING hybrid evaluation– multiplicity effects to be tested by embedding
Proof of Hybrid Approach Applicability
pT = 3 GeV/c pT = 4 GeV/c pT = 5 GeV/c
pT = 6 GeV/c pT = 7 GeV/c pT = 8 GeV/c
pT = 9 GeV/c pT = 10 GeV/c
Oct.14, 2009
12/12Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki
with ID
new physics prospects at very high pT at LHC ALICE at LHC starting in months (finally!) neutral meson yields in first year very promising
– both for p+p and Pb+Pb runs real issue: S/B ratio, significance S/(S+B)
– especially for multi-body decays (e.g. , K0s) in Pb+Pb
0 feasible even in central Pb+Pb work in progress: , , K0
s
– solid basis on RHIC experiences physics from very beginning of LHC operation!
Summary and Concluding Remarks
Oct.14, 2009
13/12Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki
discard highly asymmetric pairs to reduce BG– background concentrated at high (
asymmetry)
– acceptance only at low at low pT
– optimized for 0: < 0.7 at pT 3 GeV/c
– two photon separation only at high at very high pT
minimum cut option
more complicated cuts for > 2 body cases– e.g. 0–0 energy asymmetry in K0
s case
Famous Kinematic Cut: Asymmetry
Oct.14, 2009
14/12Hawaii ’09 – First High pT Physics Prospects with PHOS at ALICE – K.Shigaki