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

qq