Heavy Ions at the LHC

Peter G. Jones

University of Birmingham, UK

NP UK Community Meeting, Cosener’s House, 10-11 September 2008

Peter G Jones, NP UK Community Meeting 2008 2/12

LHC Status•First beam circulated yesterday!

•Short proton-proton run at 900 GeV, then ramp to 10 TeV.

•Full energy: 14 TeV (protons), 5.5 TeV per nucleon (Pb ions).

•Normal running: ~7 months protons, ~1 month Pb ions per year.

Geneva

French Alps

ALICE, Point 2

(1.15 PeV or 0.18 mJ per ion)

Peter G Jones, NP UK Community Meeting 2008 3/12

ALICE - Vital Statistics

ITSLow pt trackingVertexing

ITSLow pt trackingVertexing

TPCTracking, dEdxTPCTracking, dEdx

TRDElectron IDTRDElectron ID

TOFPIDTOFPID

HMPIDPID (RICH) @ high pt

HMPIDPID (RICH) @ high pt

PHOS,0 PHOS,0

MUON -pairs MUON -pairs

PMD multiplicityPMD multiplicity

16 metres high, 26 metres long, and ~10,000 tonnes

Peter G Jones, NP UK Community Meeting 2008 4/12

ALICE – Observables•ALICE is a general purpose detector

Access to a wide range of observables in one experiment!

Peter G Jones, NP UK Community Meeting 2008 5/12

ALICE - Main Features•Excellent tracking and PID capabilities.

•High resolution tracking from 0.2 – 300 GeV/c.

•Powerful particle discrimination.

Peter G Jones, NP UK Community Meeting 2008 6/12

Birmingham – Profile in ALICE•History of involvement in CERN experiments since mid-1980s

NA36 (Jones, Nelson)

NA49 (Barnby, Jones, Nelson)

WA85 (Evans*, Kinson, Villalobos-Baillie)

WA94 (Evans, Kinson*, Villalobos-Baillie)

WA97/NA57 (Bombara, Evans, Kinson, Lietava, Villalobos-Baillie)

•Birmingham’s role in ALICE

Responsible for ALICE trigger system.

Only major subsystem owned wholly by a single university group.

Seat on Management and Technical Boards.

Strong involvement in the science (Physics Performance Reports).

Now one of the largest groups in ALICE.

Currently preparing for first (early pp) physics.

* = spokesperson

Peter G Jones, NP UK Community Meeting 2008 7/12

ALICE – Trigger•Features

Up to 60 inputs (every 25 ns)

24 L0 – 100 ns decision time

24 L1 – 1 s decision time

12 L2

50 trigger classes

Inputs, detectors,

past/future protection,

rare/not rare …

6 detector clusters

4 past/future protections

•Rates

Pb-Pb collisions: 8 kHz interaction rate (L = 1027 cm-2s-1)

p-p collisions: 200 kHz interaction rate (L = 31030 cm-2s-1)

David Evans / ALICE trigger

Peter G Jones, NP UK Community Meeting 2008 8/12

ALICE - Key Physics•Study QCD on its natural (energy) scale T > TC ≈ QCD.

•Explore quark and gluon dynamics in a hot medium.

•Hot topics:

Collective behaviour – flow.

Opacity to jets – energy loss (gluon bremsstrahlung).

Heavy flavour production.

•Some new theoretical developments:

AdS/CFT correspondance – gravity dual.

Connection between string theory ...

… and strongly-coupled gauge theories.

Provides an alternative to (lattice) QCD.

Some (limited) success so far.

K

l+

l–

jets

b

cc

b

Peter G Jones, NP UK Community Meeting 2008 9/12

New ideas in Hadronization

David d'Enterria (CERN)David Evans (Birmingham)Nick Evans (Southampton)Nigel Glover (IPPP)Peter Jones (Birmingham)Frank Krauss (IPPP)Kasper Peeters (MPI)Marija Zamaklar (Durham)

David d'Enterria (CERN)David Evans (Birmingham)Nick Evans (Southampton)Nigel Glover (IPPP)Peter Jones (Birmingham)Frank Krauss (IPPP)Kasper Peeters (MPI)Marija Zamaklar (Durham)

Peter G Jones, NP UK Community Meeting 2008 10/12

ALICE – proton-proton physics•ALICE has a competitive programme of pp physics

Precision measurements of (total) cross-sections.

Particle production as a function of pT.

Data on fragmentation functions.

Study of diffractive events.

Probes nucleon structure.

•Advantages of ALICE

Low transverse momentum coverage.

Particle tracking.

Particle identification.

•More speculative …

Multiplicity: pp (LHC) = CuCu (RHIC)

QGP in pp collisions?

p + p 0 + Xp + p 0 + X

Peter G Jones, NP UK Community Meeting 2008 11/12

UK – ALICE Physics•First (proton-proton) physics

Multiplicity and transverse momentum distributions.

Lietava is leading one of the first physics working groups.

Initial tests of QCD; input to fragmentation functions.

Are parton distributions sufficiently well understood?

•Correction for trigger biases

Important for all papers.

•Longer term proton-proton physics – Pb-Pb physics

Resonances – sensitive to hadronic phase (Villalobos-Baillie).

Charmonium ( J/) production – Debye screening (Lazzeroni).

High-pT and jet physics – energy loss (Barnby, Bombara, Evans, Lietava).

Anomalous high multiplicity pp events – (Jones).

Peter G Jones, NP UK Community Meeting 2008 12/12

Outlook and Summary

Expect a short (1 week) Pb-run in 2009.

From 2010, 1 month of Pb per year.

First few years, Pb-Pb collisions @ 5.5 TeV per nucleon.

Option of changing beam species/energy in subsequent years.

e.g. p-Pb, symmetric light ions, lower energy(ies).

LHC will achieve first collisions very soon.

ALICE has a full physics programme.

UK is helping to shape that programme.

First physics proton-proton collisions Pb-Pb collisions.