Palaiseau Search for the SM Higgs Bosons at

Palaiseau Search for the SM Higgs Bosons at the LHC The first 1 Yves Sirois Y. Sirois, LLR Ecole Polytechnique -1 fb LLR Ecole. Polytechnique D 0 Meeting, Paris - 10/2008 CNRS-IN 2 P 3

Opening Remarks (1) Palaiseau • Electroweak and Strong Interactions: Yang-Mills quantum field theory with local gauge SU(3) SU(2) U(1) symmetries Symmetry groups gauge bosons Representation (arbitrary) particles Chiral structure of matter, i. e. different EW quantum numbers for R and L chiralities of the fermions forbids mass terms need a EW symetry breaking • A spontaneous symetry breaking preserves renormalisibility in EW sector while giving masses to the Z and W bosons (short range weak interaction) and maintaining a null mass for the (infinite range of electromagnetism) SM Mecanism doublet of scalar fields under SU(2) one physical boson of mass MH 2 = 2 v 2 with v = ( 2 GF)-1/2 ~ 246 Ge. V [Fermi scale] • Focus here: the road towards Higgs boson(s) discoveries at low LHC luminosities For the measurements needed to establish that a signal actually is due to the quanta of the scalar field responsible for EW symmetry breaking (in SM or MSSM or beyond) like MH, SCP, gauge couplings, self-coupling etc. . talk by K. Jacobs (this workshop) Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008

Opening Remarks (2) Palaiseau • The Standard Model SU(3) x SU(2) x U(1) of EW and Strong interactions is remarkably confirmed by experiments since many decades … The SM Lagragian is the most general that is compatible with the symmetries … and conserves the leptonic and baryonic quantum numbers (as observed) … but it is incomplete and unsatisfactory ! • Fermions acquire a (arbitrary) mass by interacting with the scalar field (with arbitrary couplings) … the stucture and family replica, etc. remain unexplained • The Higgs boson allows to regulate the calculations towards high energies … and allows to contemplate a quasi-unification (unification) of couplings at some Grand Unification scale more symmetries new bosons (interactions) • The H mass has to be stabilized at EW scale (hierarchy problem) talk by B. Heinemann (this workshop) Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008

Why the LHC ? Palaiseau The search and discovery of the Higgs Boson(s) remains a most important motivation* for the LHC scientific adventure It is an essential and necessary ingredient of the current understanding of matter and fundamental interactions It most likely lies on the critical path towards new territories (hierarchy, SUSY, GUT …) * besides producing micro black holes to swallow sub-primes (and the earth) and thus resolve the economy crisis Y. Sirois, LLR Ecole Polytechnique You mean all that thing does D 0 Meeting, Paris - 10/2008 is crack wallnuts ? ? …

The Higgs Boson and Unitarity Palaiseau Reminder: Unitarity Constraint Without a Higgs boson: theory valid for E < 1. 2 Te. V With the Higgs boson: theory valid if MH < 780 Ge. V/c 2 To avoid unitarity violations (scattering probability > 1) … the Higgs Boson must be discovered … or a new physics at the Te. V scale Needed: EW ~ 500 Ge. V q ~ 1 Te. V spp ~ 14 Te. V Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008

Theory The Higgs Boson Palaiseau SM Reminder: 1 doublet of Higgs Fields 1 physical boson (CP-even) MH is a free parameter … MH 2 = 2 v 2 ; v ~ 246 Ge. V K. Riesselman, hep-ph/9711456 Theoretical Contraints: Unitarity: ‘‘Triviality’’ (Higgs self-coupling remains finite : ) Trivialité Zone Interdite ‘‘Stability’’ Zone Permise of vacuum: Stabilité = cut-off scale Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008 Zone Interdite

Theory Higgs Boson and ‘‘Fine-Tuning’’ Palaiseau Kolda & Murayama, JHEP 7(2000)35 MH > 2 M Z disfavoured by indirect constraints (radiative corrections) Domain favored by experiments Y. Sirois, LLR Ecole Polytechnique MH excluded by direct searches at LEP D 0 Meeting, Paris - 10/2008

Theory Higgs Boson and ‘‘Fine-Tuning’’ Palaiseau Kolda & Murayama, JHEP 7(2000)35 Disfavoured MH > 2 M Z défavorisé par les contraintes indirectes (corrections radiatives) (Indirect Exclusion; 95%CL) Domaine favorisé par l’expérience Excluded (direct) Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008 MH exclu par recherches directe au LEP

The Higgs Boson and the LHC Production Modes and Cross-sections H 0 Production Excluded CTEQ 6 M, Mt=175 Ge. V used for PTDR Disfavoured BSM Physics can change these in a major way !!! (e. g. bb. H in MSSM) Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008 Palaiseau

3 From Chicago to Geneva Evolution of the Cross-Sections LHC Tevatron Palaiseau e. g. SM gg H avec H ZZ*, WW* BR acc. ~ 50 Tevatron Ratio of Higgs to EW cross-sections favorable ! W, Z tt s g g Hi Ratio of EW cross-sections to QCD favorable ! [background “candles”] Relative increase of the t t background e. g. H ZZ* 4 l l=e, MH = 150 Ge. V/c 2 H ZZ* BR acc. ~ O(10) fb QCD ~ 1014 fb Y. Sirois, LLR Ecole Polytechnique Need a ‘‘inhuman’’ reduction of 1013 ! Higgs @ LHC state of the art of ‘‘hadron collider’’ and ‘‘rare decay D 0 Meeting, Paris - 10/2008 techniques’’

3 The Higgs Boson at the LHC Observability Palaiseau A. Djouadi, hep-ph/0503172 MH 145 Ge. V H b b Dominant mode … but crippling QCD background … may be exploitable in the associated mode H t t ? H Exploitable at low MH in the VBF production mode BSM Physics can change these in a major way !!! (e. g. , bb in MSSM) H Complementary mode at low MH via loop diagrams, low BR but excellent /Jet ( ID, Iso. , M ) separation MH > 125 Ge. V Y. Sirois, LLR Ecole Polytechnique H WW(*) Dominant mode, l l channel optimal for MH = 2 MW ; l qq’ channel exploitable at large MH or through VBF H ZZ(*) Small BR but ‘‘golden mode’’ for a discovery l l D 0 Meeting, Paris - 10/2008

The Higgs boson and the LHC Le LHC Palaiseau pp spp = 14 Te. V Needed: EW ~ 500 Ge. V q ~ 1 Te. V spp ~ 14 Te. V ‘‘ Start-up Low Luminosity’’ L = 1032 cm-2 s-1 1 fb-1 Nominal ‘‘Low Luminosity’’ 30 fb-1 L = 1033 cm-2 s-1 10 fb-1/year Nominal ‘‘High Luminosity’’ 300 fb-1 L = 1034 cm-2 s-1 100 fb-1/year s. LHC L = 1000 fb-1/year Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008

CMS and ATLAS The Experiments Palaiseau ATLAS CMS Si actif: 200 m 2 LAr : 175 k canaux Tracking 2. 5, B 4 T • Si pixels and strips Calorimetry em 2. 5 had 5 • EM: homogeneous Pb. WO 4 crystals • HAD: Cu-Zn/scint. + Fe/Quartz Muon Spectrometer 2. 7 • Solenoïd return yoke instrumented Y. Sirois, LLR Ecole Polytechnique Tracking 2. 5, B 2 T • Si pixels and strips • Transition radiation detector Calorimetry 5 • EM: sampling; Pb/LAr accordeon • HAD: Sampling Fe/scint. + Cu-W/LAr Muon Spectrometer 2. 7 • Air-core toroids with muon chambers D 0 Meeting, Paris - 10/2008

From dream to reality: Palaiseau CMS Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008

From dream to reality: Palaiseau ATLAS Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008

Detector Commissioning with Cosmics Real Data ! September 10 Cruzet 4 Cruzet 3 Cruzet 2 Cruzet 1 Transverse IP residuals Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008 Palaiseau

SM Commissioning with First Data Monte Carlo 10 pb-1 W Palaiseau Z Cross-section ‘‘Measurements’’ ‘‘SM expectation’’: Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008 CMS PAS 2007/002 CMS PAS EW 08 -005

SM Commissioning with First Data Monte Carlo 10 - 100 pb-1 Entries t t + jets Palaiseau Di-lepton 100 pb-1 10 pb-1 M 3 (Ge. V/c 2) Expected Precision for the cross-section in the di-lepton channel for 100 pb-1 / = 4(stat) 4(syst) 2(pdf) 5(lumi) % Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008

SM Commissioning with Early Data Monte Carlo WZ 300 pb-1 CMS Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008 Palaiseau

e. g. Discovery Reach (Overview) Palaiseau Inclusive Channels: PTDR 2006 VBF Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008

e. g. Discovery Reach (Overview) Palaiseau Inclusive Channels: PTDR 2006 Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008

Higgs boson at the LHC H WW(*) 2 l 2 Inclusive Modes Palaiseau SM Higgs can be discovered in H WW* over a wide mass range Most sensitive around MH ~ 2 x MW [MH ~ 170 Ge. V excluded at Tevatron 95% CL] Background: NLO Event Selection: Y. Sirois, LLR Ecole Polytechnique Reducible tt, Wbt, W+jet(s) with fake leptons Irreducible WW* continuum MH=160 2. 3 pb WW*¨Cont. tt 114 pb 840 pb 2 isolated leptons at high enough PT mid-range Etmiss Central jet veto Small ll (e. g. ll 45°) Max Mll D 0 Meeting, Paris - 10/2008

Higgs boson at the LHC H WW(*) 2 l 2 e. g. cut-based analysis Inclusive Modes CMS Note 2006/047 Results essentially unchanged from previous studies with fast simulation Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008 Palaiseau

Higgs boson at the LHC H WW(*) 2 l 2 Main data-driven emphasis on Inclusive Modes Control of top background / jet veto systematics Control of lepton fake rates from data (use QCD di-jets etc. ) Masterize MVA technique already at start-up ! Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008 Palaiseau

e. g. Discovery Reach (Overview) Palaiseau Inclusive Channels: PTDR 2006 Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008

Higgs boson at the LHC The ``Golden Mode’’ : H 4 l Inclusive Modes H ZZ(*) ee CMS Palaiseau Signal: 4 e, 4 , 2 e 2 (2 x) Narrow resonance, low background Background: Reducible: t t , Zb b Irreducible: continuum ZZ(*) Selection: 4 isolated emerging from primary vertex 2 pairs of matching flavours and opposite signs caution: 4 Beware of lepton efficiency at very low PT !!! Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008

Higgs boson at the LHC H 4 l Analysis (PTDR) Inclusive Modes Palaiseau Analysis assuming optimal performances with ∫L d. L = 30 fb-1 CMS-Note 2006/136 Here shown: signal and background at the L required for a 5 discovery CMS Note: • Les corrections NLO pour le continuum ZZ(*) dépendent de M 4 l • Le bruit est soit mesuré des ‘‘side-bands’’, soit déduit par normalisation ZZ/ Z Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008

Higgs boson at the LHC H ZZ* 4 l at low L Inclusive Modes Palaiseau Emphasis on: • Control/optimize lepton measurement and lepton isolation efficiencies (use Z in tag-and-probe) … go for the highest which is just sufficient !) • Very low PT leptons (>50% below 10 Ge. V/c for MH=130 Ge. V/c 2) need to combine tracking and calorimetry (internal/external detectors) for e (mu) • Must get MH right by the time we arrive to first hints • Not enough side-bands ! better predict ZZ* continuum from measured Z … but need a good understanding of ZZ* shape (and there are non-trivial gg ZZ* contributions of up to 20%) • A full analyses at start-up luminosities ∫L d. L = 1 fb-1 assuming realistic 100 pb-1 detector knowledge and performances show capability of almost full suppression of tt and Zbb backgrounds event even at low MH (exploit more stringent cuts on the least isolated/lowest PT leptons) Expect: between 1 and 10 signal events observed (depending on MH) with S/B from in the range 2 to 4. • Sanity checks: relax flavour and sign requirements and exploit combinatorial Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008

Electrons and photons at the LHC Not so … transparent ! CMS ATLAS The electrons initiate showers (e. g. 40 -80%) Identification and efficiency problems, charge mis-identification The photons convert (e. g. 20 -40%) in e e pairs before reaching the ECAL Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008 Palaiseau

e. g. Discovery Reach (Overview) Palaiseau Inclusive Channels: PTDR 2006 Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008

Higgs boson at the LHC H Inclusive Modes Signal: Solenoïd Mode rare: Br ~ 2 10 -3 Recherche d’un pic étroit sur un fond (localement) ~ plat HCAL ECAL Important à basse masse BR 99 65 fb MH = 115 140 Ge. V/c 2 Silicon Tracker Bruit de fond: Irréductible: 2 réels (Born + box diagrams) Muon System CMS-Note 2006/112 Y. Sirois, LLR Ecole Polytechnique Palaiseau D 0 Meeting, Paris - 10/2008 Réductible: 1 réel QCD di-jets + + jet(s)

Higgs boson at the LHC H Inclusive Modes Palaiseau CMS-Note 2006/112 Suppression du bruit de fond ID et Isolation Signal x 10 MH = 120 Ge. V/c 2 L = 7. 7 fb-1 Propriétés du bruit de fond mesurées dans les ‘‘side-bands’’ Signal x 10 Coupure NN relâchée Coupure NN forte Réseau de Neurones exploitant classification des photons (S/B par événement) + propriétés spéficiques du signal (implicite PT , , VBF/gg, …) Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008 MH = 120 Ge. V/c 2 L = 7. 7 fb-1

Higgs boson at the LHC H preliminary Palaiseau H+ETmiss+ 1 l S/B 2 tt. H WH inclusive S/B . 03 preliminary H+1 j S/B . 08 VBF + more jets with gg H preliminary Y. Sirois, LLR Ecole Polytechnique preliminary H+ETmiss S/B 2 ZH WH Different S/B for different sub-channels H+2 j Divide and Conquer strategy S/B . 4 VBF mainly D 0 Meeting, Paris - 10/2008 33

Higgs boson at the LHC H Palaiseau L required for a 5 discovery: CMS NN: Kinematics + photon categories Small systematics on background (side-bands) Note: ~ 20% uncertainty on expected signal) Y. Sirois, LLR Ecole Polytechnique Combined fit: selection observables + photon catagories D 0 Meeting, Paris - 10/2008

Higgs boson at the LHC Vector Boson Fusion (VBF) Palaiseau Zeppenfeld et Rainwater (1997) Jet vers l’avant Forward (quark) jet tags (jet veto in central region) Higgs boson decay products in central region (trigger) Higgs boson gets a PT kick ’s generally not back-to-back Modes de désintégration étudiés: qq (V V*) qq’H; H (l ) (l- ) (l ) (jet ) H H WW* (l )(l- ) (l )(jet jet’) Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008 M : possible via e. g. approx. colinéaire pour les produits de désintégration des (si les ne sont pas acolinéaires) … résolution dépendant de ETmiss

Higgs boson at the LHC e. g. Discovery Reach (Overview) Palaiseau Higgs discovery potential in VBF with 30 fb-1 qq. H, H→ →lj: 4 s 115 -145 Ge. V qq. H , H→ : 2 s 115 -135 Ge. V qq. H , H→WW→l jj: 5 s 140 -200 Ge. V High L in talk by K. Jacobs (this workshop) Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008 36

3 Le Boson de Higgs au LHC VBF H Palaiseau H H • Queue de Z dans la zone du signal (e. g. pour MH < 130 Ge. V) Contrôle à partir des données en utilisant des vrai/faux Z construit à partir d’événements réel Z en remplaçant les par une simulation MC de Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008

Z mass shape from Z data Palaiseau VBF selection: Mjj >400 Ge. V, Dhj 1 j 2 >2. 5 pt >10 Ge. V |h |<2. 4 70<M <110 Ge. V Inclusive Drell-Yan Higgs boson signal in tail of Z peak: understanding DY di-t mass shape important Y. Sirois, LLR Ecole Polytechnique Uncertainty dominated by modeling of Etmiss (pileup, underlying event, calor. noise & response, …) Z events : ’s substituted by simulated ’s with ’s kinematics to model background shape D 0 Meeting, Paris - 10/2008 38

Expected mass distribution for 1 fb-1 Palaiseau Relaxed VBF selection for 1 fb-1 analysis 1 fb-1 Analysis 30 fb-1 Analysis >2. 5 >4. 2 Mj 1 j 2>0. 4 Te. V Mj 1 j 2>1 Te. V j<2. 2 Full di- mass using collinear approximation of neutrinos from the decays and the visible decay products Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008 39

Expected Exclusion limits for 1 fb-1 of data Palaiseau Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008 40

We have seen Cosmics … Palaiseau D 0 Meeting, Paris - 10/2008 e. g. Cosmic Muon Slicing … … through CMS Y. Sirois, LLR Ecole Polytechnique

We have seen the LHC beam … Palaiseau Y. Sirois, LLR Ecole Polytechnique 10 September 2008 D 0 Meeting, Paris - 10/2008

The very first beam-splash event from the LHC in Palaiseau ATLAS on 10: 19, 10 th September 2008 Online display Offline display D 0 Meeting, - 10/2008 43 Status. Paris of ATLAS PJ Y. LHCC, Sirois, 24 -Sep-2008, LLR Ecole Polytechnique 43

Halo Muons in CSCs and HB Palaiseau CMS Center Meyrin CMS Centre Meyrin Beam pîck-up monitors First beam through CMS ! Y. Sirois, LLR Ecole Polytechnique Jim CMS Center Meyrin Virdee D 0 Meeting, Paris - 10/2008 Fabiola Gianotti

We have seen Higgs CMS Experiment Palaiseau Peter Higgs visiting the LHC in April 2008 Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008 Peter Higgs

Palaiseau We are eagerly awaiting for the first collisions ! Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008

Higgs Boson announcement Freely adapted from P. Grannis D 0 Workshop Palaiseau Higgs discovery to be announced at a CERN seminar* by CMS and ATLAS * open-air field rented to a local farmer Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008

Higgs Boson announcement Palaiseau Higgs discovery to be announced at a CERN seminar* by CMS and ATLAS * open-air field rented to a local farmer Are there lessons (e. g. for BSM in Run 2) ? * Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008 … always blame the machine for delays

Disclaimer Palaiseau In this talk: assume standard LHC configurations at 14 Te. V Consider knowledge (detector systematics, backgrounds) in steps of integrated luminosities at 10 pb-1 100 pb-1 … 1 fb -1 Y. Sirois, LLR Ecole Polytechnique D 0 Meeting, Paris - 10/2008