The LargeHadronCollider- adream thathas become...

The Large HadronCollider - adream thathas becomerealityLuisa CifarelliDipartimento di Fisica, Universitadi Bologna, Italy

TuesdaY,3 May - 11:15 a.m,

The origin oftheLarge Hadron Coll ider(LHC) at CERNnearGeneva hasfar-reachingroots.The LHCproject, designandconstructionoverseveral decades isanexemp lary achievement in fundamentalphysicsresea rch.Iwill explainthemodeof operationof theLHC, pointing out theadvantages of beambeam colliders over accelerators with fixed targets andalso addressingthecharacteristicsof hadroncolliders vs. electron-positron colliders.

The world epochal records oftheLHC in tenns ofenergy andluminosity- togetherwith itsmarvellousdetectors conceived withtop-technology components- areenabling beautiful experiments. Iwillpresent a paradeofsuch detectors andofsomeof the impressive measurements andresultssofarobtained. Iwill finally sketch a few ofthepossible surprises thattheLHC mighthave instore.This talkwillprovideunderstanding ofthefantastic role forthe LHC at thedawn ofa new era forscience andknowledge.

Happy 25th anniversary EPL !!!

1986 1997

2007

2011

First proposal for a European Letters Journal formulated in 1980 under the EPS Presidency of A. Zichichi (1978-1980)

Initiative of a collective European effort to harmonize physics publications in Europe to create a high-quality letters journal that would publish the best communications on new physics wherever it was done, be it Europe or worldwide

Final partnership agreement signed in March 1985 under the EPS Presidency of J. H. Stafford (1984-1986)

Angela Oleandri(SIF Editorial Director and Memberof the EPLA Board of Directors)


Presidents:SIF – R.A. RicciSFP – M. Jacob

IOP – A. Merrison

<< After years of the most thorough discussions on the needs, the means, the structure, the people … during which the physics community of Europe through the EPS Divisions and the national societies has been fully consulted, EPS is able to formally announce the publication from 1 January 1986 of a new fortnightly journal:

EUROPHYSICS LETTERS (EPL)

incorporating Journal de Physique Lettresand Il Nuovo Cimento Lettere

With these words – published on the front page of the June 1985 issue of Europhysics News – the journal venture officially started >>


1986Partners for initial investment: SFP – SIF – IOP – EPS

supported by other national societiesPublishers: Les Editions de Physique (EDP) – SIFMerger of 2 letters journals: Journal de Physique Lettres –

Lettere al Nuovo CimentoEditorial Office @ EPS Headquarters (Geneva) with scientific

background and control by EPSProduction @ SIF (Bologna)Printing and distribution @ EDP (Paris)1st Editor-in-Chief: N. Kurti1st Chairman of Management Board: W. Buckel (EPS)

Initial unexpected success !!!Among authors of the first issues in 1986-1988:C. Jarlskog, E. Fiorini, R.L. Mössbauer, O. Poulsen, C. Cohen-Tannoudji,

J. Dalibard, A. Aspect, P.G. De Gennes, G. Parisi, M. Virasoro, A. Coniglio, H. Whal, S. Gozzini, F. Bassani, V. Degiorgio, A. Paoletti,

J.C. Sens, A. L’Huillier, M. Leduc, J.M. Gaillard, F. Iachello, L. Pietronero, V. Dose, UA1 …


Happy 25th anniversary EPL !!!In EUROPHYSICS LETTERS Volume 1, Number 7, April 1st 1986, p. 327-345 UA1 Collaboration – Intermediate-vector-boson properties at the CERN Super Proton Synchrotron ColliderAbstract. – The properties of a sample of 172 charged intermediate vector bosons decaying in the (eνe

) channel and 16 neutral intermediate vector bosons decaying

in the (e+e–) channel are described. …Note from the Editor-in-Chief

Our readers may have noticed with surprise that the length of the preceding paper is more than twice the agreed maximum. The paper was judged by three referees to be of the right character and quality for it to be published in Europhys. Lett. After discussion with two Co-editors and the referees it was agreed to accept the paper as an exceptional measure without cuts.

It was thought that shortening the paper by removing some of the information it contained would have greatly impaired its usefulness. ... We had to admit that here was a case where the results of the sustained collaborative effort of a large number of scientists and engineers could not be compressed into the space normally allocated to a paper. This decision was approved, although not unanimously, by the Editorial Board in retrospect.

However, we want to emphasize that this departure from the norm should not be regarded as a precedent, but rather as a very rare exception.

N. KURTI

Through the 1990s and at the turn of the century/millenium17 societies participating in the journal1996: online version of EPL hosted by EDP Sciences1997: creation of EPLA (Geneva) since EPS Headquaters

moved from Geneva to Mulhouse in 1996 under H. SchopperEPS Presidency1997: change of publication frequency and of cover of the

journal

2004: EPL Editorial Office moved from Geneva to Mulhouse under M. Ducloy EPS Presidency

… however some slowdownwith respect to initial success

2007: relaunch with new format and new cover


High Energy (HE) Particle Physics – also called Subnuclear Physics – addresses the question of understanding the structure of matter at the most fundamental level, at the smallest scale of size

Thanks to large accelerators and colliders, particles can be produced and the interactions among their elementary constituents studied in the laboratory

Thanks to large and highly performing detectors, measurements can be performed with extreme precision

Subnuclear/HE Particle Physics

The LHC (Large Hadron Collider)presently working at CERN in Geneva

will allow the study of matter constituents and their interactions at unprecedented levels of

energies ever reached so far

LHC

Subnuclear/HE Particle Physics

Large Hadron Collider (LHC)

The Large Hadron Collider (LHC) has been designed to accelerate beams of protons that can collide at energies up to √s = 14 TeV (7 TeV/beam)

It also allows to accelerate and make collide beams of ions (nuclei), in particular Pb nuclei (Pb82+ ions) at energies up to √sNN

= 5.5 TeVhigh temperature & energy density

QGP/QGCW

At present LHC is working as:p-p collider at √s = 7 TeV (3.5 TeV/beam)Pb-Pb collider at √sNN = 2.76 TeV

Particle accelerators & colliders

Particle accelerator: facility that allows to produce beams of particles with high kinetic energy

Charged particles (electrons, protons, ions/nuclei) are accelerated, guided and confined along well defined trajectories by means of electromagnetic fields

First accelerators were electrostatic (Cockcroft-Walton, Van de Graaff)single acceleration step ΔVmax~10-20 MVcontinuous beam of particles

High energy accelerators use instead alternate electric fields with:a series of sequential acceleration stepspulsed beam of bunches of particleslinear / circular Cockcroft-Walton

at Fermilab

Linear acceleratorSeries of cylindrical electrodes connected to an AC voltage generator (Wideröe)E = 0 inside each electrode constant velocityE = Vd between 2 contiguous electrodes acceleration

T/2

T

0

Acceleration if the traversal time through the electrodes with reversed polarity is T/2

electrodes with growing length Ln = vnT / 2

beam

AC generator

electrodes

source

(RF source)

Linear acceleratorSoon electrode length prohibitive …

increase νRF but growth of e.m. radiationinclude electrodes in a series of contiguous (in phase) “cavities”unique RF cavity system to obtain a progressive wave guide(acceleration with vphase

≈ vparticle )

Example of rectangularwave guide

Electric field

Particles are trapped in the RF voltage where they oscillate back and forth in time/energy (RF cavity = resonator tuned to a selected frequency)

bunch structure of beams

Magnetic field

Circular accelerator: synchrotronBeam maintained on an orbit of constant radius R

acceleration at each turn (orbit)by means of magnets positioned along the circumference

magnetic field increasing with energy to keep particles on orbit

qvB = m v2

R

B = mvqR

Lorentz force

magnets

accelerating RF cavity

Storage ring and colliderSpecial type of synchrotron: with injected beams accelerated and maintained on orbit at the desired energy

Two beams circulating in opposite directions colliding in different intersection points where the experimental setups (detecors) are positioned

After each interaction the beams remain in orbit for further collisions

acceleratingRF cavities

magnets

intersection points(detectors)

Cycle of a collider

injection

acceleration

stable beams & collisions

Ecm2 = �P fascio� Ptarghetta�2

= �E fascio�mc2�2− p2c2

= 2 m2 c4�2 mc2 E fascio

�2mc2 E fascio

Fixed target(proton beam on proton target)

Ecm= �2mc2 E fascio

Ecm2 = �P fascio1� P fascio2�

2

= 2 m2 c4�2 E fascio2 �2p2 c2

= 4 E fascio2

Collider(two colliding proton beams)

Ecm= 2 E fascio

Advantage of a collider

fascio = beamtarghetta = target

Energy and luminosity

The luminosity is determined by the collider parameters

N n. of particles/bunchn n. of bunches in orbitf collision frequencyσx σy

beam dimensions

L = N 2nf4πσ xσ y

FHigh luminosity is essential to study rare phenomena

(F = suppression factor (0.8-0.95) depending on beam crossing angle & divergence)

LHC parameters

LHC – yet another collider?The LHC surpasses existing accelerators/colliders in 2 aspects :

The energy of the beam of 7 TeV that is achieved within the size constraints of the existing 26.7 km LEP tunnel.

LHC dipole field 8.3 T

HERA/Tevatron ~ 4 T

The luminosity of the collider that will reach unprecedented values for a hadron machine:

LHC pp ~ 1034 cm-2

s-1

Tevatron pp 3x1032 cm-2

s-1

SppbarS pp 6x1030 cm-2

s-1

The combination of very high field magnets and very high beam intensities required to reach the luminosity targets makes operation of the LHC a great challenge !

A factor 2 in field

A factor 4 in size

A factor 30in luminosity

J. Wenninger, LNF Spring School, May 2010

LHC accelerator system

Proton source

Electric discharge in plasma chamber ionization of hydrogen

Ion extraction 90 keV

LINACLinear accelerator

for protons from source up to 50 MeV

PSB, PS and SPS

PSB Proton Synchrotron Booster 50 MeV 1.4 GeVPS Proton Synchrotron 1.4 GeV 26 GeVSPS Super Proton Synchrotron 26 GeV 450 GeV

After a first LINAC acceleration protons are further accelerated by a cascade of synchrotrons each increasing the energy by about one order of magnitude so as to reach the desired beam injection energy of LHC (450 GeV)

LHC tunnel & magnetsInstalled in the LEP tunnelSubdivided in 8 sectors4 interaction points~ 1200 dipole magnets, ~ 400 quadrupole magnets: superconducting, frozen at 1.9 K (superfluid liquid He)2 vacuum pipes with beams circulating in opposite directions inside the same magnet (two-in-one design)

Dipole length ~ 15 mI = 11800 A @ 8.3 T

Rüdiger Schmidt

Beam tube

Superconducting coil

Non-magnetic collars

Ferromagnetic iron

Steel cylinder for Helium

Insulation vacuum

Supports

Vacuum tank

Weight (magnet + cryostat) ~ 30 tonslength ~ 15 m J. Wenninger, LNF Spring School, May 2010

LHC RF systemThe LHC RF system operates at 400 MHz.

It is composed of 16 superconducting cavities, 8 per beam.

Peak accelerating voltage of 16 MV/beam.

For LEP at 104 GeV : 3600 MV/beam !

Synchrotron radiation loss

LHC @ 3.5 TeV 0.42 keV/turn

LHC @ 7 TeV 6.7 keV /turn

LEP @ 104 GeV ~3 GeV /turn

The nominal LHC beam radiates a sufficient amount of visible photons

to be actually observable !(total power ~ 0.2 W/m)


LHC contains 9300 magnets(dipoles, quadrupoles, sextupoles, octupoles,

decapoles)1232 of them are superconducting dipoles(14.3 m, 8.3 T, 35 t) kept at the temperature of 1.9 K = -271.3 °C

less than the temperature of cosmic space (2.7 K) !!!

All superconducting dipoles are kept in a bath of superfluid liquid He @ 1.9 K, atmospheric pressure

LHC ha 36800 t of mass to keep cold !!!

Some numbers …

LHC vacuum is 10-13 atm10 times lower than on the Moon !!!

(in a volume of 6500 m3 ≈ like a cathedral)

At LHC the acceleration from 450 GeV to 7 TeVlasts ~ 20 minutes with an average energy gain of ~ 0.5 MeV/turn

Pb nuclei (Pb82+ ions) are produced and acceleratedat LHC at 5.5 TeV/nucleon pair

centre of mass energy of 1150 TeV

1 TeV ≈ the kinetic energy of a mosquito in flight !!! What is extraordinary at LHC is the fact that this energy is

concentrated in a space about 10-12 times < than a mosquito !!!

Some numbers …

Some numbers …

View of the LHC tunnel

Recollecti ons about

LHC

Recollections about LHC

ECFA LEP “White Book” 1979

In the ECFA LEP “White Book” 1979

LEP (1989-2000)e+e- 100–209 GeV

D = 5 m LHC (2009- ...)pp 14 TeV & PbPb 5.5 TeV/NN pair

LHC History1982 : First studies for the LHC project

1983 : Z0/W discovered at SPS proton antiproton collider (SppbarS)

1989 : Start of LEP operation (Z/W boson-factory)

1994 : Approval of the LHC by the CERN Council

1996 : Final decision to start the LHC construction

2000 : Last year of LEP operation above 100 GeV

2002 : LEP equipment removed

2003 : Start of LHC installation

2005 : Start of LHC hardware commissioning

2008 : Start of (short) beam commissioning

Powering incident on 19th Sept.

2009 : Repair, re-commissioning and beam commissioning

2010 : Start of a 2 year run at 3.5 TeV/beam


LHC and Subnuclear/HE Particle Physics COORD

INATIO

N in EU

: CERN Council and ECFA

(European Com

mittee for Future A

ccelerators)

http://council.web.cern.ch/council/en/E

uropeanStrategy/ESParticlePhysics.htm

l

Geneva, 22 April 2011 – PRESS RELEASE Around midnight this night CERN’s Large Hadron Collider set a new world record for beam intensity at a hadron collider when it collided beams with a luminosity of 4.67 x 1032 cm-2s-1. This exceeds the previous world record of 4.024 x 1032 cm-2s-1, which was set by the US Fermi National Accelerator Laboratory’s Tevatron collider in 2010, and marks an important milestone in LHC commissioning.

Enter a New Era in Fundamental ScienceEnter a New Era in Fundamental ScienceStart‐up of the Large Hadron Collider (LHC), one of the largest and truly global scientific projects ever, is the

most exciting turning point in particle physics.

Start‐up of the Large Hadron Collider (LHC), one of the largest and truly global scientific projects ever, is the

most exciting turning point in particle physics.

Exploration of a new energy frontier Proton-proton collisions at ECM

up to 14 TeVExploration of a new energy frontier

Proton-proton collisions at ECM up to 14 TeV

LHC ring:27 km circumference

TOTEM LHCfMOEDAL

CMS

ALICE

LHCb

ATLASR. HeuerErice School 2010

LHC – Science and Planning

Main physics goals

Test the untested (scalar) sector of the Standard Model: spontaneous breaking of the EW symmetry and generation of the particle massesSearch for new physics at the TeV scaleIdentify (some of) the particle(s) that make up the

majority of the Universe (SuperSymmetry ?)Explore the QCD phase diagram with nucleus-nucleus

collisionsTest precision physics of B (especially strange

beautiful mesons)… Discover the UNEXPECTED

Short and long range planning for LHCPhysics run started 30 March 2010 @ 3.5+3.5 TeVPhysics run in 2010-2012 @ 3.5+3.5 TeV

(decide about slightly higher energy later on)Shutdown 2013 to prepare LHC towards 7+7 TeV

(Cu stabilizer consolidation, He-release valves, . . .)Physics run in 2014-2015 @ 7+7 TeV and up to 2020

@ design luminosity 1034 cm–2s–1 [Lint 300 fb–1]Around 2017 start major improvements of LHC

luminosity and detectors performanceHigh Luminosity LHC (HL-LHC) @ ~5 x 1034 cm–2s–1

from 2020 up to 2030 [Lint = 3000 fb–1 in 10 years]

LHC – Science and Planning

[n. of collisions per unit of cross section: 1 μb=10–30 cm2 – 1 pb=10–36 cm2 – 1 fb=10–39 cm2]

2011 pp √s=7 TeV

2010 pp √s=7 TeV

2010 PbPb √sNN

=2.76 TeV

LHC integrated luminosity

[n. of collisions per unit of cross section:1 μb=10–30 cm2

– 1 pb=10–36 cm2 – 1 fb=10–39 cm2 ]

ATLAS (IP-1) A Toroidal LHC ApparatuS

ATLAS

C. Issever, Open LHCC Session, 23 March 2011J. Zhang, XIX International Conference on DIS and Related Subjects, 4 April 2011L. Vacavant, SLHC-PP Meeting, 8 March 2011

The largest detector ever builtGeneral purpose detector to allow the study of a large variety of high energy phenomena, with a large potential for new physics discoveriesHermetic detector with cylindrical geometry (barrel+endcaps) consisting of a complex system of subdetectors to identify electrons, muons, hadrons, jets, etc. and measure their momentum and energy

Length: 46 mHight: 25 mWidth: 25 mWeight: 7000 t

Results based on electrons, muons, jets, b-tagging, Etmiss:

Standard Model(soft QCD, prompt photons, B, W / Z, jets, top, …)

Higgs searchSUSY and other exotics searches

(leptoquarks, 4th generation quarks, extra gaugebosons, compositeness ...)

Eiffel towerweight: 7500 t

Di-muon invariant mass spectrum

Di-electron invariant mass spectrum

International Linear Collider (ILC)Site: to be determined in the next phase of the project Community: nearly 300 laboratories and universities around the world: more than 700 people are working on the accelerator design, and another 900 people on detector development. Energy: up to 500 GeV with an option to upgrade to 1 TeVAcceleration Technology: 16,000 superconducting accelerating cavities made of pure niobium Length: approximately 31 km

A TESLA nine-cell 1.3GHz superconducting niobium cavity

ILC RoadmapSteps to a Project – Technical (2-3 years)

– R&D for Risk Reduction and Technology Improvement– Systems Tests– Engineering Design + Industrialization

Project Implementation– Government Agreements for International Partnership– Siting and site-dependent design– Governance

Time to Construct– 5-6 years construction + 2 years commissioning

Project Proposal / Decision keyed to LHC results

ILC could be doing physics by early to mid- 2020s

Electron-positron collider consisting of two linear accelerators that face each other.

A study for a future electron-positron collider aiming at a center-of-mass energy range of 0.5 to 5 TeV, optimised for a nominal center-of-mass energy of 3 TeV

Compact Linear Collider (CLIC)

CLIC multi-lateral collaboration40 Institutes from 21 countries

2011-2016 – Project Preparation phaseGoal: preparation of a (staged) Project Implementation Plan (PIP) at reviewed energy and luminosity (taking into account results of CDR and based on Physics requests as soon as available…)

After 2016 – Project Implementation phaseGoal: Lay the grounds for full approval and preparation of the technical documentation needed for moving into (staged) construction following Physics requests (which should be known by the time….)

At EPS Conference:kick-off meeting to update the European Strategy for Particle Physics (2006)

Finalized by September 2012

Highest-mass dijet event recorded in 2010

Run 167607 Event 9435121Dijet Minv

=4 TeV ET

miss=31GeV

Soft QCD: pp inelastic cross sectionMeasurement of pp inelastic cross section for ξ > MX

2/s > 5 x 10–6

σinel = 60.3 ± 0.05(stat) ± 0.5(syst) ± 2.1(lumi) mb

Extrapolation to full ξ rangeConsistency with theoretical predictions

Top cross section and mass

Lepton+jets and dileptondecay channels

Excellent agreement with Standard Model predictions

σtt-bar = 180 ± 9(stat) ± 15(syst) ± 6(lumi) pb

Search for SM Higgs boson production(Brout-Englert-Higgs-Guralnik-Hagen-Kibble boson)

Search for Standard Model Higgs

H0 γγ

mH = 110–140 GeV

H0 ZZ 4l, llνν, llqqmH

= 200–600 GeVH0 WW(*) lνlν, lνqq

mH = 120–200 GeV (*)

mH = 200–600 GeV

Excluded from direct searches: LEP mH

<114.4 GeVTevatron 158 < mH

< 173 GeV

Excluded if 4th sequential high mass fermion generation:Tevatron 131 < m < 204

Exclusion limit for 200 GeV < mH

< 600 GeV:

Fit parameter μ = σ/σSM(i.e. μ = 1 SM prediction)

95% CL upper limit means:σSignal

< μ x σSM x BR(H0 WW)

H0 WW lνqq

Search for Higgs boson H0 WW lνqq

Most sensitive channel at presentfor 120 GeV < mH

< 200 GeVBest exclusion limit at 95% CL:cross section < 1.2 x σSMat mH

=160 GeV

Search for Higgs boson H0 WW* lνlνExciting 2011 ahead of ATLAS with 3 fb–1

Exclusion (95% CL) 120 GeV < mH

< 500 GeVEvidence (3σ)

130 GeV < mH < 450 GeV

Discovery (5σ)150 GeV < mH

< 175 GeV

H0 WW* lνlν

… catching up with the Tevatron soon

Events with 0 leptons+Etmiss+jets

Interpretaton in phenomenological simplified MSSM

If m=m(squark)=m(gluino), exclude m < 870 GeVExclude m(gluino) < 500 GeV

Search for SUSY

Events with 1 lepton+Etmiss+jets

Interpretaton in mSUGRA

Reach well beyond LEP and Tevatron

Most stringent limits to date

(sfermion )

(gau

gino

)

CMS (IP-5) Compact Muon Solenoid

CMS

G. Dissertori, Open LHCC Session, 23 March 2011L. Benhabib – F. Pandolfi – F. Ma – W. Quayle – M. Chiorboli, Moriond QCD, 20-27 March 2011C. Veelken, Moriond EWK, 14 March 2011M. Stoye, SLHC-PP Open Event, 8 March 2011

Compact detector built arounda huge superconducting solenoidal magnet (B = 4 T)Like ATLAS, CMS is a general purpose detector that will allowto study a large variety of expected and unexpected phenomenaIt consists of a tracking system, electromagnetic and hadronic calorimetersand muon detectors

Length: 21 mHeight: 15 mWidth: 15 mWeight: 12500 t

Results based on electrons, muons, jets, b-tagging, Etmiss:

Standard Model(jets at high / low pT

, heavy quarks, W/Z, …)Higgs searchSUSY and other exotics searches

(leptoquarks, 4th generation quarks, extra gauge bosons, compositeness ...)

Heavy ions (PbPb)

Rediscovery of Standard Model

Di-muon invariant mass spectrum

Jet cross section – Benchmark test of pQCD

Di-jet cross sectionData / theory compatible with inclusive jet measurement

Inclusive jet cross sectionGood agreement with prediction over > 10 orders of magnitude

Summary of various inclusive top pair production cross section measurements in 7 TeV pp collisions

In 2010: ~ 1000 tops in CMS+ATLAS

Top cross section and mass

Z0 τ+τ production

Z τ+τ production analyzed in 4 channels: μ+τhad, e+τhad, e+μ, μ+μ

σ x BR(Z/γ* τ+τ–) = 1.00 ± 0.05(stat) ± 0.08(sys) ± 0.04(lumi) nb

Measured Z τ+τ cross section in good agreement with measured Z l+l– (l = e/μ) cross section and with theory predictions (NNLO)

Search for MSSM Higgs boson(s)

Stringent limits on MSSM Higgs well beyond Tevatron reach(consistent with analogous ATLAS results)

(φ: pseudoscalar+scalar Higgs of ~ same mass)

H ττ, ντ

Search for SM Higgs boson H0 WW* lνlν

Excluded 144 < mH < 207 GeV/c2

(consistent with analogous ATLAS result)

95% CL mean expected and observed upper limits on the cross section σH

x BR(H WW* 2l2ν) for masses in the range120-600 GeV/c2

Results obtained using a Bayesian approach Expected cross sections for SM and for SM with a 4th fermion family (SM4)

Search for SUSYEvents with 0 leptons + Et

miss + jets Interpretaton in cMSSM

Events with 1 lepton + Etmiss + jets

Interpretaton in cMSSM

Extended previously explored range of model parameters(in agreement with ATLAS)

Road-map for discoveries set up

Z0 μ+μ– in PbPb at √sNN = 2.76 TeV

Z0 e+e– in PbPb at √sNN = 2.76 TeV

Z boson production in PbPb collisions

Z l+l– signal is essentially unaffected by the strongly interacting medium produced in PbPb collisionsZ production is a reference for processes modified by the medium such as quarkonia production, etc.Precise measurement of Z production in heavy ion collisions can help to constrain nuclear PDFs

LHCb (IP-8)LHC-beauty

LHCb

F. Teubert, LHCC Meeting, 23 March 2011A. Golutvin, CERN RRB, April 2011

Experiment focused on the study of quark-b (beauty) physics and on the study of rare decays and phenomena of hadrons containing quark-b

LHCb is an experiment made of a single arm spectrometer positioned in the forward region with respect to the interaction region

LHCb is using LHC as an “intensity frontier” machine rather than an “energy frontier” machineto explore quark flavour physics

Due to LHCb acceptance, trigger and detector resolution, the experiment is already competitive with Tevatron (in future with e+e- B factories)


Results on:- Production studies (σb

, W / Z …)- Bs

mixing phase- Bs,d μμ- Bd K*μμ- Measurement of the angle γ of the

Unitarity Triangle (reconstruction of hadronic B decays)

- CP violation studies in charm sector

LHCb physics programmeThe main LHCb physics goal is to find evidence for new physics through the indirect effect that new degrees of freedom may have on B (beautiful b-mesons) and D (charmed c-mesons) decaysThis search is complementary to direct searches and provides information on masses, couplings, spins and CP phases

Search for super rare Bs,d μμ

Bs,d μμ can access new physics through new virtual particles entering in the loop, in particular the decay is sensitive to new MSSM scalar and/or pseudoscalar interactions

B+ → J/ψ( → μμ) K+ Bs

→ J/ψ(→ μμ) φ( → K

+K–) Bd → K+π–

BR(Bs μμ) < 4.3(5.6) x 10-8 @ 90(95)% CL [Exp. 6.5 x 10-8 @ 95% CL] BR(Bd μμ) < 1.2(1.5) x 10-8 @ 90(95)% CL [Exp. 1.8 x 10-8 @ 95% CL]

Already close to best Tevatron limits

First observation of B0s D0 K*0

First observation of B0s J/ψ f0

Nsignal = (111 ± 14) events

12.8 σ significance

Probes of CP-violating new physics effects in oscillation box diagramsB0

s-B0s mixing phase measured using B0

s J/ψ φ, B0s J/ψ f0

Probes of CP-violating new physics effects in so far unexplored penguin diagrams in Bs system CP asymmetries measured in B0

s φ φ and B0s K*0 K*0

First observation of B0s K*0 K*0

Nsignal = (34.5 ± 7.4) events

7.37 σ significance

ALICE (IP-2) A Large Ion Collider Experiment

ALICE

B. Guerzoni, IFAE 2011, 27-29 April 2011P. Giubellino, CERN RRB, April 2011A.Dainese, Rencontres de Physique, La Thuile, March 2011

Detector optimized for the study of nuclear collisions at extreme energies with thousands of low momentum particles/event are produced

B = 0.5 TLarge tracking system to allow chargedparticle track reconstruction with ~150 points/trackA powerful and large system of particle identification (PID) detectorsSingle arm muon spectrometer in the forward region


Results in PbPb:Multiplicity, flow, high-pT

suppression, di-hadron correlations, strangeness and heavy flavours, quarkonia, …

Results in pp:Multiplicity, pT

spectra, correlations, strangeness, heavy flavours, particle ratios …

Space‐time Evolution of the Collisions

eγ

space

time jet

Hard Scattering + Thermalization(< 1 fm/c)

PbPb→

Expan

sion

→ Hadronization particle composition is fixed (no more inel. Collisions)

p K πφ

Freeze-out(~ 10 fm/c) (no more elastic collisions)

Λμ

QGP (~ few fm/c)

γ e

Quark Gluon Coloured World QGCW

commonly called QGP

Quark Gluon Plasma

Deconfinement (Tc ~170 MeV) in PbPb

How hot is it? 100 000 times the temperature at the center of the Sun

PID performance

π K p

e

TPC + TOF

TOF

TOFTPC

Charged-particle multiplicity measurement in proton-protoncollisions in the central rapidity / pseudorapidity regionpp @ √s= 0.9, 2.36, 7 TeV

pp collisions

Energy density from dNch/dηLHC PbPb @ √sNN

=2.76 TeV

dNch /dη = 1599 ± 4(stat) ± 80(syst)

100 times cold nuclear matter density

~3 times the density reached at RHIC AuAu @ √sNN

=0.2 TeV(ε ≈ 15 GeV/fm3)

Central PbPb collisions

Volume and lifetime from Hanbury-Brown & Twiss (HBT) interferometry

freeze-out volume ~300 fm3

~2 times the volume measured at RHIC AuAu @ √sNN

=0.2 TeVlifetime up to freeze-out ~10 fm/c

Volume

Lifetime

Jet quenching in PbPbRatio RAA =

n. of particles in AA (PbPb) collision per NN (binary) collision

n. of particles per pp collision

Strong suppression of high-pT hadrons in PbPb collisionsparton energy loss: jet quenching

New feature: evolution of RAA as a function of pTNew constraint for parton energy-loss models

Elliptic flow in Pb-Pb at 2.76 TeV

Collective behavior observed in Pb-Pb collisions at LHC

Similar to RHIC almost ideal fluid at LHC ?

New input to the energy dependence of collective flow

Di-hadron correlations in PbPb and “ridge”

Low / intermediate pTnear-side “ridge” in Δηbroad, flat away-side

study ridge evolution, hydrodynamics vs. quenching

High pTnear-side dominates but no ridgequenching / suppression on away-side

study parton energy loss

AzimuthalCorrelation~ 180 deg

AzimuthalCorrelation~ 180 deg

Leading particle

Leading particle

~ Low pT

High pTAway-side correlation at LHC seems weaker than at RHIC …

Di-hadron correlation powerful tool to study medium

Anti-Alpha 4He candidates in PbPb

Thank you for your attention

Thanks to F. Bellini and B. GuerzoniPbPb √sNN

= 2.76 TeV

ATLAS pp @ 7 TeV

Study of Jet Quenching in HI collisions at CMS

arXiv:1102.1957

For pT >120 GeV/c in central PbPb collisions at √sNN

=2.76 TeV a factor 2 suppression of balanced di‐ jets is observed ‐> recoiling jets interact significantly with the medium

CMSp-p@7 TeV

The LargeHadronCollider- adream thathas become...

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