(New) Physics at the LHC Fabiola Gianotti (CERN) Status of machine - PowerPoint PPT Presentation

(New) Physics at the LHC Fabiola Gianotti (CERN)  Status of machine and experiments, experimental challenges  The first year(s) of data taking  Longer-term physics potential (examples …)  Constraining the underlying theory F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 1

• pp √ s = 14 TeV L design = 10 34 cm -2 s -1 (after 2009) LHC L initial ≤ 2 x 10 33 cm -2 s -1 (until 2009) • Heavy ions (e.g. Pb-Pb at √ s ~ 1000 TeV) TOTEM (integrated with CMS): TOTEM (integrated with CMS): pp, cross-section, diffractive physics pp, cross-section, diffractive physics ATLAS and CMS : ATLAS and CMS : pp, general purpose pp, general purpose TOTEM 27 km ring (previously used for LEP) Here: ATLAS, CMS First collisions : summer 2007 ALICE : ion-ion, p-ion LHCb : pp, B-physics, CP-violation F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 2

 Status of machine and experiments 836 out of 1232 superconducting dipoles (B=8.3 T) produced as of last Friday Magnet quality is very good F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 3

110 dipoles installed in the underground tunnel as of last Friday F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 4

Dipole interconnections Cryoline successfully cooled down last week Such a high-tech machine requires sophisticated tests … Dipole installation in the tunnel F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 5

Not only dipoles …. Inner triplet quads assembly Dipoles 1232 Quadrupoles 400 Sextupoles 2464 Octupoles/decapoles 1568 Orbit correctors 642 Others 376 Total ~ 6700 Assembly of Short Straight Session F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 6

LHC injection lines: 5.6 km, 700 magnets 23/10/2004: first beam injection test from SPS to LHC through TI8 transfer line F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 7

LHC physics goals Search for the Standard Model Higgs boson over ~ 115 < m H < 1000 GeV. Explore the highly-motivated TeV-scale, search for physics beyond the SM (Supersymmetry, Extra-dimensions, q/l compositness, leptoquarks, W’/Z’, heavy q/l, etc.) Precise measurements : -- W mass -- top mass, couplings and decay properties -- Higgs mass, spin, couplings (if Higgs found) -- B-physics (mainly LHCb): CP violation, rare decays, B 0 oscillations -- QCD jet cross-section and a s -- etc. …. Study phase transition at high density from hadronic matter to quark-gluon plasma (mainly ALICE). Etc. etc. ….. F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 8

The environment and the experimental challenges  Don’ t know how New Physics will manifest → detectors must be able to detect as many particles and signatures as possible: e, µ , τ , ν , γ , jets, b-quarks, …. → ATLAS and CMS are general-purpose experiments. Excellent performance over unprecedented energy range : few GeV → few TeV tt → bW bW → bl ν bjj event from CDF data (b) W - b-tagging (secondary vetices) τ (b-hadrons) ~ 1.5 ps → decay at few mm from primary vertex → detected e+ W + with high-granularity Si detectors Jet 4 (b) ν F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 9

 Event rate and pile-up (consequence of high luminosity …) Event rate in ATLAS, CMS : N = L x σ inelastic (pp) ≈ 10 34 cm –2 s –1 x 70 mb ≈ 10 9 interactions/s Proton bunch spacing : 25 ns Protons per bunch : 10 11 2 5 n s detector ~ 20 inelastic (low-p T ) events (“minimum bias”) produced simultaneously in the detectors at each bunch crossing → pile-up Impact of pile-up on detector requirements and performance: -- fast response : ~ 50 ns p p T θ -- granularity : > 10 8 channels -- radiation resistance (up to 10 16 n/cm 2 /year in forward calorimeters) -- event reconstruction much more challenging than at previous colliders F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 10

 Huge (QCD) backgrounds (consequence of high energy …) q High-p T QCD jets g g q q W, Z W, Z q g H Higgs m H =150 GeV t g ~ q ~ ~ g ~ q , g pairs m ~ 1 TeV q ~ q g • No hope to observe light objects (W, Z, H ?) in fully-hadronic final states → rely on l, γ • Fully-hadronic final states (e.g. q* → qg) can be extracted from backgrounds only with hard O(100 GeV) p T cuts → works only for heavy objects • Mass resolutions of ~ 1% (10%) needed for l, γ (jets) to extract tiny signals from backgrounds • Excellent particle identification: e.g. e/jet separation F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 11

ATLAS • • Tracking (| η |<2.5, B=2T) : -- Si pixels and strips Length : ~45 m -- Transition Radiation Detector (e/ π separation) Radius : ~12 m Weight : ~ 7000 tons • Calorimetry (| η |<5) : Electronic channels : ~ 10 8 -- EM : Pb-LAr … and 3000 km of cables … -- HAD: Fe/scintillator (central), Cu/W-LAr (fwd) • Muon Spectrometer (| η |<2.7) : air-core toroids with muon chambers F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 12

CMS • • Tracking (| η |<2.5, B=4T) : Si pixels and strips Length : ~22 m Radius : ~7 m • Calorimetry (| η |<5) : Weight : ~ 12500 tons -- EM : PbWO 4 crystals -- HAD: brass/scintillator (central+ end-cap), Fe/Quartz (fwd) • Muon Spectrometer (| η |<2.5) : return yoke of solenoid instrumented with muon chambers F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 13

August 25 2005: an historical day at Point 1 and Point 5 Point 1: 8 th (and last) ATLAS barrel toroid installed in the underground cavern F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 14

2 Point 5: 5 A u g u s t 2 CMS magnet (230 tons, L=12.5 m, R=3m) rotated from vertical 0 0 5 to horizontal position before insertion into cryostat (operation at T=4.2 K) F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 15

CMS end-cap Muon Spectrometer All 400 CSC chambers produced, > 60% installed F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 16

ATLAS inner tracker: insertion of the third Silicon layer (out of four) into the barrel cylinder F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 17

Tower energies: ~ 2.5 GeV First cosmic muons observed by ATLAS in the underground cavern on June 20th (recorded by hadron Tilecal calorimeter) F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 18

Examples of expected performance Muon momentum resolution expected in CMS Electron E-resolution measured in beam tests of ATLAS EM calorimeter σ / E 9.4% / √ E ⊕ 0.1% 1 TeV µ ± : 1 TeV e ± : σ (E)/E ≈ 0.5% σ (p)/p ≈ 5% KK resonance M c = 4 TeV in TeV -1 ED µ + µ - Heavy narrow resonances will likely e + e - be discovered in the X → ee channel (muon decay useful for couplings, asymmetry, etc.) m(l + l - ) GeV F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 19

 The first year(s) of data taking First collisions (Summer 2007) : L ~ 5x 10 28 Plans to reach L ~ 10 33 in/before 2009 Hope to collect few fb -1 per experiment by end 2008 Total statistics from Channels (examples …) Events to tape for 1 fb -1 previous Colliders (per expt: ATLAS, CMS ) ~ 10 4 LEP, ~ 10 6 Tevatron W  µ 7 x 10 6 µ ν Z  µ µ ~ 10 6 µ µ ~ 10 6 LEP, ~ 10 5 Tevatron tt  W b W b  µ µ ν +X ~ 10 5 ~ 10 4 Tevatron g ~ ~ g m = 1 TeV 10 2 - 10 3 With these data: • Understand and calibrate detectors in situ using well-known physics samples e.g. - Z → ee, µµ tracker, ECAL, Muon chambers calibration and alignment, etc. - tt → bl ν bjj jet scale from W  jj, b-tag performance, etc. • Measure SM physics at √ s = 14 TeV : W, Z, tt, QCD jets … (omnipresent backgrounds to New Physics) → prepare the road to discovery ……. it will take a lot of time … F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 20

Example of initial SM measurement : top signal and top mass (relevant to New Physics …..) Bentvelsen et al. ATLAS 150 pb -1 • Use gold-plated tt → bW bW → bl ν bjj decay ( < 20 days at 10 32 ) • Very simple selection: -- isolated lepton (e, µ ) p T > 20 GeV -- exactly 4 jets p T > 40 GeV -- no kinematic fit -- no b-tagging required (pessimistic, assumes trackers not yet understood) • Plot invariant mass of 3 jets with highest p T B=W+4 jets (ALPGEN MC) Events Stat. error Stat. error M (jjj) GeV Time δ M top (GeV) δσ / σ at 10 33 1 year 3x10 5 0.1 0.2%  top signal visible pretty soon with 1 month 7x10 4 0.2 0.4% simple selection cuts and no b-tagging  cross-section to ~ 20% 1 week 2x10 3 0.4 2.5%  top mass to ~7 GeV  get feedback on detector performance Ultimate LHC measurement precision: (jet E-scale, b-tag) m top to ~ 1 GeV (and m W to ~ 15 MeV)  tt is background to many searches F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 21

What about early discoveries ? Three examples …. An easy case : a new (narrow) resonance of mass ~ 1 TeV decaying into e + e - , e.g. a Z’ or a Graviton → e + e - of mass ~ 1 TeV An intermediate case : SUSY A difficult case : a light Higgs (m H ~ 115 GeV) F. Gianotti, GGI Inaugural Conference, Arcetri, 19/09/2005 22