CMS Heavy Ion Physics
-
Upload
ivan-hartman -
Category
Documents
-
view
31 -
download
1
description
Transcript of CMS Heavy Ion Physics
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 1
HI
CMS Heavy Ion PhysicsPablo Yepes
Rice University
Hadronic CollisionsQuarkonia ProductionJet Collisions
Coherent Interactions
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 2
HIWhy HI at LHC
Jurgen Shukraft, Quark Matter 2001
SPS RHIC LHC
dNch/dy 500 800 3000
Vf(Kfm3) 1 7 20 Bigger
(GeV/fm3) 2.5 5 20 Hotter
QGP(fm/c) 1 3 7 Longer
0(fm/c) 1 0.5 0.2
Pb+Pb, central collisions (b=0)
Pb Pb
Before
After
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 3
HIJ/Melting
L(fm): Average distance travel by the J/ inside tNuclear Matter.
J/
Yie
ld
u,d u,d
c c Hadrongas
J/K+
-
u,d u,d
c cQGP
ud
d
NA50 Collaboration, CERN
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 4
HIQuarkonia Acceptance in CMS Chambers
10%
20%
Acc
epta
nce
J/at CMS
Upsilon at CMSPt(GeV)
Full Detector
Full Detector
Barrel
Barrel
•CMS: J/ mainly pT>5 GeV with barrel, due to cutoff. •ALICE: >2.5 with •ATLAS (if they do HI) lower acceptance due to higher pT cutoff.
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 5
HI Quarkonia Reconstruction
Essential sub-detectors:Tracking devices Muon system
Pessimistic assumptions for background estimates:dNch/dy=8000
(most generators < 5500)<pt>GeV/c (HIJING
0.39 GeV/c)<pt>k=0.67 GeV/c
Special Heavy Ion Tracking AlgorithmSignificant Muon background from and K decays
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 6
HIJ/ Signal 1 month running
at top Luminosity: J/’s detected and reconstructed in the Barrel:
Ca-Ca Pb-Pb
# J/ 2.2 105 104
S/B 9.7 1.0
103
104
2 2.25 2.5 2.75 3 3.25 3.5 3.75 4 4.25 4.5
Min bias collisions - 1 month run - barrel onlymuons with P > 3.5 GeV/c
Pb-Pb
/cont.= 1.0
# ev
ents
/25
MeV
/c2
104
105
2 2.25 2.5 2.75 3 3.25 3.5 3.75 4 4.25 4.5
Ca-Ca
/cont.= 9.7
Opposite-sign di-muon invariant mass (GeV/c2)
L= 2.5 1029 cm2 s-1
# ev
ents
/25
MeV
/c2
L= 1027 cm2 s-1
ALICE: ~2K events with s
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 7
HI
1 month: 22000 and 7500
’ detected in the barrel
Upsilon in Pb-Pb
Opposite-sign di-muon Invariant Mass (GeV/c2)Background contributions
1022
1033
104
8.5 8.75 9 9.25 9.5 9.75 10 10.25 10.5 10.75 11
L= 1027 cm-2 s-1
Total
Decay-Decay Decay-b
Decay-c
b-b
c-c
Upsilon/cont.= 1.6
# E
ven
ts/2
5 M
eV/c
2
0
1000
2000
3000
4000
5000
6000
7000
8.5 8.75 9 9.25 9.5 9.75 10 10.25 10.5 10.75 11
Di-muon Invariant Mass (GeV/c2)
# E
ven
ts/2
5 M
eV/c
2
Combinatorial background subtracted after reconstruction
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 8
HIUpsilon in Ca-Ca
103
104
105
8.5 8.75 9 9.25 9.5 9.75 10 10.25 10.5 10.75 11
Opposite-sign di-muon invariant mass (GeV/c2)
L= 2.5 1029 cm-2s-1
Total
Decay-Decay
Decay-b
Decay-c
b-b
Upsilon/cont.= 9.4
# E
ven
ts/2
5 M
eV/c
2
• 1 month:
• 340000 • 115000 ’
• Only barrel used.
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 9
HI
Upsilon’/Upsilon ratio as a
Thermometer(Ramona Vogt)
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 10
HIQuarkonia Reference
At SPS, J/ is compared to Drell-Yan.
At LHC Drell-Yan contribution is negligible.
Z0 proposed as reference to production.MZ>M
Different production mechanisms: Z0: antiquark-quark, quark-gluon and
antiquark-gluon. : gluon-gluon.
Cross check di-muon reconstruction algorithm
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 11
HIJet Quenching
• Large pT quarks affected by hot hadronic media
• Jets at RHIC buried in low pT background• Look at particle pt spectrum
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 12
HIJets at LHC are Easy for High Multiplicity PbPb
monojet/dijet enhancement jet-Z0or jet-
dNch/dy=8000
Tot
al C
alor
imet
er E
nerg
y
Jet Finding100 GeV ET
-~100%- (ET)/ET=11.6%.
Jet quenching
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 13
HIBalancing Photons and Jets
Etjet,
120GeV in the barrel
1 month:900 events
for Pb-Pb104 events
for Ca-Ca
# E
ven
ts/4
GeV
ET//0-ET
Jet (GeV)
<E>=8 GeV<E>=4 GeV<E>=0 GeV
Background
2 weeks at L=1027 cm-2s-
1
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 14
HIUltra Peripheral Collisions(Coherent Interactions)
Low pT pT < 1/R 50 MeV
Low Energy ECMMax < /R
CERN SPS ECMMax =0.5 GeV
RHIC ECMMax =6 GeV Detected
CERN LHC ECMMax =160 GeV
A
A orP
orP
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 15
HISTAR Ultra-Peripheral Event
(DNP 2000)
End view
AuAuP (Au)
Trigger: Low multiplicity and zero energy at Zero Degree Calorimeter (ZDC)
Side view
ZDC ZDC
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 16
HI Physics
New Physics:Standard Model H production marginal for HIAny exotic particle coupling to . Supersymmetric Higgs for some areas of parameters space.
Mainly studied at e+e- colliders.Typically 0<mc. tot up to 70 GeV by LEP.
Non perturbative QED, coupling Z2.
Ethr
(GeV)
(Pb+Pb)(barn)
(Ca+Ca)(barn)
0.5 1,500 5.5
1.0 500 1.8
5.0 30 0.1
e+e- Cross Sections
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 17
HI
even
ts/s
ec/G
eV
10-14
10-12
10-10
10-8
10-6
10-4
10-2
100
10-1 100 10 10210-12
10-10
10-8
10-6
10-4
10-2
10
102
AA
(bar
n)
even
ts/s
ec
M (GeV)
f2
a2
f2'ccc0c2
b
0bb
HSM
H'
10-5
10-3
10-1
10
103
105
107
even
ts/y
ear
1 10 102
M (GeV)
1014
1012
1010
108
106
104
102
1
10-12
10-10
10-8
10-6
10-4
10-2
1
102
AA
(M)
(bar
n/G
eV)
hadrons
e+e-
-
cc
bb
10-5
10-3
10-1
10
103
105
107
even
ts/y
ear/
GeV
Ultra-Peripheral Collisions Cross Sections
Meson orlepton/quark pair
A
AA
A
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 18
HI Physics, Hadron Spectroscopy
Heavy quark spectroscopy. Very large numbers expected
Light quark: Difficult at CMS because of low pT, challenge for triggering, unless a multiplicity trigger is used.
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 19
HIPhoton Nucleus (A)
p studied in HERA: Wp<200 GeV
A at LHC: Wp<900 GeV
Vector meson production: p(A) Vp(A), V=,J/Very large rates, for example >104 Hz in Ca-CaInterface QCD and hadronic physicsLHC will be a meson factory. Competitive with other meson
factories like factory at Frascatti (CP, QM tests, etc).Can CMS trigger on these events. Clean events with only a
few tracks.
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 20
HIConclusions
CMS is provides unique tools to study Heavy Ion Collisions at LHC.
Some physics topics:Quarkonium production: and J/ families.Jet quenching. Ultra-Peripheral collisions.
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 21
HIAddendum: Tracking
Developed for dNch/dy=8000 and dN0/dy=4000.
Track only particles with tracks in detector.
Use -chambers tracks as seeds.
Use only tracking detector providing 3D space points.
Occ
up
ancy
(%
)
0
10
20
30
40
50
60
60 70 80 90 100 110 120
Detector Pitch m
MSGC 200
MSGC 240
Silicon 147
Radius of MSGC layer (cm)
May 19, 2001May 19, 2001.
Pablo Yepes, Rice U 22
HIInterference
Nuclei can emit or scatter pairtwo indistinguishable possibilities
Amplitudes addVector meson has negative parity
~ |A1 - A2eip·b|2
Destructive interference when pT << 1/b