Electroweak Physics at the LHC Alessandro Ballestrero Introduction

Electroweak Physics at the LHC Alessandro Ballestrero • Introduction • EW and QCD • W mass measurement • W production • Two boson production • Boson scattering and unitarity • EVBA : extrapolation and deconvolution? • Boson Scattering and Gauge Invariance • PHASE Monte Carlo • Boson Fusion and Higgs • Conclusions Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 1

Introduction what we expect from LHC Higgs and SUSY is the most common answer Higgs as a scalar poses problems (quadratic divergences) if we admit a physical cutoff in theory SUSY removes this cutoff far away (to the Plank scale) and solves the problems of fine tuning But if we admit that SM is valid only up to a certain scale, other possible scenarios are also possible: no Higgs , dynamical symmetry breaking, technicolor, . . . Moreover we cannot exclude new phenomena that we do not expect Electroweak physics is requested for accurate theoretical predictions They will be important for precision physics higgs searches and measures of its properties, establishing possible deviations from standard model, evaluating backgrounds to all searches for any kind of new physics. Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 2

EW and QCD LHC is an hadronic collider. Strong interactions will be dominating: • αS ten times bigger than αem • gluons more abundant than quarks in protons • also quarks prefer to interact via QCD. But the distinction between Strong and Electroweak physics is somewhat artificial: They are complementary and are both necessary to the understanding of SM and BEYOND Consider top production and top mass measurement: • 90% It is a strong process 10% (x 1 x 2 10 -3) but. . Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 3

EW and QCD • Cross section determined to NLO precision -Total NLO(tt) = 834 ± 100 pb (largest uncertainty from scale variation) 107 tt at low luminosity LHC is a top factory ! low lumi 10 fb-1 high lumi 100 fb-1 Lepton side This will allow to reach 1 Ge. V (in one year? ) precision in top mass measurement Hadron side Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 4

EW and QCD but. . Alessandro Ballestrero top mass has a strong influence on electroweak precision predictions via ew corrections. The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 5

EW and QCD Data fitted : • The Z parameters - lineshape and lepton asymmetry at LEP: m. Z ΓZ σh Rl and Al. FB - Ae and Aτ from τ polarization at LEP - Al from polarised left-right asymmetry by SLD - Heavy quark (b and c) measurementes at LEP and SLD: Rb Rc Ab. FB Ac. FB Ab Ac - sin 2 θleff from quark forward-backward asymmetry at LEP • W mass m. W at LEP and Tevatron • Top mass m. T at Tevatron • sin 2 θW from νN scattering data by the Nu. Te. V experiment A=g. V g. A /(g. V 2 + g. A 2) = asimmetry right left Input parameters for the calculations: α (m. Z) m. Z Gμ αS (m. Z) mt mh ( for the corrections ) Parameters of the fit: m. Z mt mh αS (m. Z) and Δαh(5) (m. Z) Alessandro Ballestrero (light quark contribution to running of alfa) The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 6

EW and QCD uncertainties (both theoretical and experimental) are generally big. so if we can isolate ew contributions these will in generally give a clean prediction The luminosity of LHC will allow anyhow precision measures. Hence we need in some cases QCD predictions to NNLO and NLO EW corrections to QCD observables have started to appear Maina S. Moretti Ross. . . Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 7

EW and QCD For the precise knowledge of tt cross section one should go to NNLO There are not EW corrections available for tt production They are probably not useful by themselves as tt bar productions is a much more complicated process In reality one has to deal not only with the two signal diagrams has more than 300 diagrams has more than 700 Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 8

EW and QCD Weak corrections are available for the similar process b massless Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 9

EW and QCD The same group has also analyzed Weak corrections to p p γ , Z + jet Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 10

EW logs In the following I will mainly discuss the physics of vector bosons (W, Z) production and scattering Many NLO EW calculations have been performed, and NLO MC's start to appear One must however realize that : For 4 or more fermions in the final state complete NLO EW are not available and in many cases one has to rely on approximations Leading Pole Approximation, Leading Log Approximation, Final State Radiation. . . why ew corrections can give important enhancements at high energies ? Sudakov logs corrections appear, which become important for s >> MW 2 At LHC they are of the order Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 11

EW logs SUDAKOV LOGS 2 IN A NUTSHELL Ciafaloni. . Denner. . Beenaker. . . . • Correspond to soft and collinear singularities in theories with massless bosons In that case they are canceled by real radiation • Regulated by boson mass in EW. They are finite • Real emission of EW bosons has not necessarily to be summed It is considered that a W can always be distinguished by the emitting fermion • In the Feynman gauge they are associated with virtual graphs where soft collinear bosons are exhanged between external legs • Can be computed in eikonal approximation • DL are universal: only depend on external particles Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 12

EW logs Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 13

W mass measurement Radiative corrections affect three level relations between SM parameters It is possible to determine m. H fom measuremnt of mt and m. W (sin 2 θW, , m. Z) or assess the consistency of SM predictions with precision measurements Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 14

EX CL UD ED W mass measurement indirect Status of inputs WC 2004: mt=174. 3 ± 5. 1(exp) Ge. V/c 2 m. W=80. 426 ± 0. 034(exp) Ge. V/c 2 m. Z=91. 1875 ± 0. 0021(exp) Ge. V/c 2 Z=2. 4952 ± 0. 0023(exp) Ge. V SM predictions from ZFITTER and TOPAZ 0 programs Direct and indirect data favour a light Higgs ! Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 15

W mass measurement Thanks to M. Grunewald Perspective at the LHC m. W=15 Me. V; mt=1 Ge. V (world combined will look better than these ! – Tevatron run II, LEP 2) (current central values assumed) ED CL UD Using had=0. 00012 EX SM constraints on m. H: direct ( m. H/m. H 25%) After LEP and Tevatron m. W=30 Me. V it will probably be possible to reach m. W=15 Me. V in the low lumi phase ! Alessandro Ballestrero Chances of ruling out the SM ? The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 16

W mass measurement mtop and MW: equal weight in the EW fit if MW 0. 007 mtop at LHC: mtop 2 Ge. V gives the precision MW : 15 Me. V W-pair cross-section is too low Single W: no direct determination of m. W possible because of the missing neutrino, but huge statistics ! ne W beam line transverse mass (missing p. T) W mass : fit exp. shape to MC sample with different Values of MW < 2 Me. V/y as a statistical uncertainty syst. error: MC modelling of physics and detector response Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 17

W production Drell Yan mechanism not only important to measure W mass: Rapidity distributions can provide information on PDF's Also important as a background to new phisics at high pt. Tree level is trivial Main uncertainty is due to QCD corrections (5%) expecially for transwerse momentum of W due to gluon emission. Two different types of ew. corrections: Resummation of final state radiaton in pole approximation Complete ew corrections O(α). Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 18

W production Pole approximation LPA When one has resonant diagrams e. g. p 2 – M W 2 + i Г M W one can make an expansion of the complete amplitude around the complex poles retaining only leading order (residue at the poles) Corresponds to retaining the propagator and projecting, in the rest of the computation, the two four momenta on mass shell of the decaying particle (the procedure is not univoque) It is a gauge invariant procedure (which is not considering only resonant diagrams) This approximation can be taken at any order in perturbation theory Normally it is not used at tree level but as a useful approximation for. NLO corrections Famous example: Ew corrections to four fermion processes at e+ e- computed in double pole approximation Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 19

W production Resummation of final state radiation in pole approximation YFS exponentiation WINHAC Placzek Jadach Pavia shift extimate with a "pseudo experiment" HORACE Carloni Calame Montagna Nicrosini Alessandro Ballestrero exponentiation The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 20

W production Combined effect of QCD Resummation and QED radiative corrections NLO QED included in RESBOS Cao and Yuan Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 21

W production Complete ew corrections O(α) single Z p p Z l+ l- single W p p W l ν O(α) parton cross section ZGRAD 2 Baur Hollikl Wackeroth. . . Dittmaier Kramers contain mass singuraties α ln(mq) These collinear singularities are reabsorbed in PDF This is done with Absorption would require inclusion of O(α) corrections in DGLAP and experimental fit to data (but the effect is well below 1%) Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 22

W production Dittmaier Kramers Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 23

W production Dittmaier Kramers Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 24

Two boson production Vector boson pair production: test for non abelian structure of SM. New physics at energies much larger than those tested at LEP 2 could modify these interactions. Effects of anomalous couplings will eventually be measured at LHC Background to new physics: Eg. chargino neutralino gold plated signal for Susy 3 charged leptons + missing p. T Full ME's and O(αS) at NLO with full spin correlations available and cross checked Dixon, Kunszt, Signer, Ellis, . . QCD corrections quite significant: increase xsect by a factor 2 (10 for high p. T ) But with a jet veto they reduce to 10% Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 25

Two boson production EW corrections only in leading log. They factorize for arbitrary process. Accomando Denner Pozzorini Computed for and for in leading log approximation (log 2 and log of S/MW) neglecting logs of other invariants ( valid for , at large angles with respect to the beam ) and non factorizable corrections. Corrections in (single or double) Pole approximations Mc has full processes and at Born level (IBA) We are still far from complete ew corrections for four fermions but in this case they are probably not needed EW corrections non negligible in the high energy region for large transverse momentum and small rapidity separation of the emitted bosons, Region of relevance for new physics effects Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 26

Two boson production Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 27

Boson scattering and unitarity WW scattering Consider longitudinally polarized W's: For single diagram proportional to: Alessandro Ballestrero ! The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 28

Boson scattering and unitarity gauge cancellations at work For the three diagrams without Higgs It still violates unitarity HIGGS RESTORES UNITARITY provided (qualitatively) Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 29

Boson scattering and unitarity More precisely : Partial wawes unitarity requires Limit on m. H and energy at which new physics should appear if m. H too large Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 30

Boson scattering and unitarity If Higgs does not exist or its mass too large, new physics must appear at Te. V scale (LHC) A signal for this is an unexpected growth with energy of WW (Boson) scattering Various theories (Technicolor, dynamical symmetry breaking) and phenomenological models have been studied All predict unexpected phenomena (e. g. formation of resonances) in Boson scattering. These are connected to new mechanisms to restore unitarity Can Boson scattering be measured at LHC ? There is a chance for it in hard processes like u s -> c d W+ W+ or ud -> ud W+ Wwhich contain contributions of the type Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 31

Boson scattering and unitarity Different ways of constructing amplitudes which satisfy unitarity constraints from low order amplitudes e. g. Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 32

EVBA : extrapolation and deconvolution ? Equivalent Vector Boson Approximation a V a A Alessandro Ballestrero V a The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 33

EVBA : extrapolation and deconvolution ? a b Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 34

EVBA : extrapolation and deconvolution ? -1 n+1 is a function of q 1 and q 2 off shell (spacelike) The approximation consists in projecting it on boson mass shell Different approximations can also be taken in evaluating the boson luminosities L(x) The approximation is valid to ~ 10% for photons, much worse for Z and W Results depend on cuts. Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 35

EVBA : extrapolation and deconvolution ? Finding information on boson scattering from experimental data needs extrapolation from q to on shell (as in EVBA) and deconvolution of the data from the integration over PDF. The energy of the WW scattering is determined by the invariant WW mass Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 36

EVBA : extrapolation and deconvolution ? Hard processes under consideration will not contain only contributions from but also from all diagrams of the type Moreover final partons are fermions with all diagrams for 6 fermion final state which depend on the final state at hand Can all this be separated from what we would like to be "the signal" ? If not, do we have anyway see consequences of EWSB pattern in these processes? Of course they will be anyhow fundamental for Higgs searches and measurements for a Higgs heavier than 140 Ge. V Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 37

Boson Scattering and Gauge Invariance We have to use complete calculations in order to • account for all irreducible backgrounds • deal with severe gauge problems and gauge cancellations A prototype of these is the extremely large interference that affects WW fusion diagrams and other diagrams with two outgoing W's. The two sets are not separately gauge invariant Their sum is gauge invariant, but only for on shell W's This huge interference casts doubts on EVBA at LHC It poses severe problems on the definition of the signal for Boson Scattering studies. Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 38

Boson Scattering and Gauge Invariance The interference A. B. Accomando. Belhouari Maina Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 39

Boson Scattering and Gauge Invariance Already known since a long time Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 40

Boson Scattering and Gauge Invariance Previous results are confirmed by PP-> u s -> d c W+ W- (on shell W's) no higgs unitary σ (pb) All diagrams 1. 86 E-2 WW fusion diagrams 6. 67 ratio ww / all 358 m_h=200 m. WW>300 unitary σ (pb) All diagrams 8. 50 E-3 WW fusion diagrams 6. 50 ratio ww / all 765 Feynman gauge has still big cancellations but about a factor 30 less than unitary! no higgs feynman σ (pb) All diagrams 1. 86 E-2 WW fusion diagrams 0. 245 ratio ww / all 13 m_h=200 m. WW>300 feynman σ (pb) All diagrams 8. 50 E-3 WW fusion diagrams 0. 221 ratio ww / all 26 Distributions show huge interference effect which are not constant: they depend very much on the value of the variable Is it possible to find regions with low interference and use it to define WW scattering signal? Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 41

Boson Scattering and Gauge Invariance all diagrams unitary WW fusion ratio unitary feynman WW fusion ratio feynman pp us dc W+WNO HIGGS ratio = WW fusion / all Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 42

Boson Scattering and Gauge Invariance all diagrams unitary WW fusion ratio unitary pp us dc W+WNO HIGGS feynman WW fusion Alessandro Ballestrero ratio feynman The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 43

Boson Scattering and Gauge Invariance Differences do not depend on Higgs NO HIGGS all diagrams ratio unitary WW fusion pp us dc W+W- Higgs M=200 Ge. V with MWW > 300 Ge. V all diagrams unitary WW fusion Alessandro Ballestrero ratio unitary The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 44

Boson Scattering and Gauge Invariance pp us dc W+W- unitary WW fusion ratio unitary t 1 all diagrams feynman WW fusion ratio feynman t 2 t 1 t 2 Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 45

Boson Scattering and Gauge Invariance t 1 a cut on MWW does not change qualitatively but worsen the ratios ratio unitary ratio feynman no cut 0. 71 0. 63 t 2 ratio feynman ratio unitary MWW > 1000 Ge. V 0. 2 2. 76 Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 46

PHASE Monte Carlo - Purpose PHASE PHact Adaptive Six Fermion Event Generator (E. Accomando, A. Ballestrero, E. Maina) Monte Carlo for LHC dedicated studies and full physics and detector simulation of Boson Fusion and scattering Higgs Production in this channel tt production Triple and Quadruple Boson Couplings Three Boson Production Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 47

PHASE Monte Carlo - Purpose The processes we have considered involve in reality 6 fermion final states They will receive contributions by hundreds of different diagrams, which constitute an irreducible background to the signal we want to examine, with all the problems connected to interferences and gauge invariance For them so far we have: • incomplete 6 fermion studies - PRODUCTION x DECAY approach (ALPGEN, COMPHEP, . . . ) most part of the analyses uses NWA and/or EVBA (PYTHIA, HERWIG) - many final states have not been considered yet • Multi-purpose Event Generators [ AMEGIC & SHERPA , COMPHEP, GRACE & GR@PPA , MADGRAPH & MADEVENT, O'MEGA & WHIZARD, PHEGAS & HELAC ] 'generic' -> 'dedicated' is not a trivial step We aim at a complete (all processes and all diagrams) and dedicated MC Full generation and simulation with high efficiency Interface to detector simulations Useful also for comparison with different approach Non irreducible backgrounds by other MC Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 48

PHASE Monte Carlo - Processes Consider l (e. g. ) in the final state We want to compute and generate in one shot all processes : Up to now only em 6 : How many are Let us consider all outgoing and fix 2 q as All processes of the type Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 49

PHASE Monte Carlo - Processes 4 W Process Initial state multipl. Boson scattering subprocess 7 diag 2 Alessandro Ballestrero 4 diag Total Number of Diagrams 202 2 x 202 2 x 202 1 x 202 The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 50

PHASE Monte Carlo - Processes 2 W 2 Z Process Initial state multipl. Boson scattering subprocess 7 diag 4 diag 2 4 diag x 422 2 x 422 2 Alessandro Ballestrero Total Number of Diagrams 422 1 x 422 The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 51

PHASE Monte Carlo - Processes Process Mixed : 4 W + 2 W 2 Z Boson scattering subprocess Initial state multip. 7 diag 2 x 7 diag 4 diag 312 2 x x 312 2 x 2 x x 312 2 x x 312 2 Alessandro Ballestrero 4 diag Total Number of Diagrams 312 The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 52

PHASE Monte Carlo - Processes how may processes and diagrams? Outgoing particles Type Diagram number Number of processes Initial mult. 2 Initial mult. 1 161 processes have different matrix elements 4 W 202 6 2 2 Z 2 W 422 10 1 2 Z 2 W 233 15 0 2 Z 2 W 422 6 2 2 Z 2 W 422 10 1 2 Z 2 W 233 15 0 2 Z 2 W 1266 3 2 2 Z 2 W 466 10 1 2 Z 2 W 1266 3 2 This only for 2 Z 2 W 466 10 1 em 6 2 Z 2 W 610 6 2 Misto 312 15 0 Misto 1046 6 2 141 20 Alessandro Ballestrero processes which differ at least for pdf: 141 x 2 + 20= 302 x 4 (CC +Fam)= 1208 The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 53

PHASE Monte Carlo - Amplitude Helicity Amplitudes written with PHACT program for producing fortran code in helicity method fast and suited for modular computing (subdiagrams) Which diagrams are effectively independent and need to be computed? Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 54

PHASE Monte Carlo - Amplitude Diagrams which belong to the same group of 8 outgoing particle can be computed in the same way Therefore do not consider 1208 or 161 but 16 different types of amplitude Many groups have identical number of diagrams. . . Outgoing particles Type Number of diagrams Number of Processes Initial mult. 2 4 W 202 6 2 2 Z 2 W 422 10 1 2 Z 2 W 233 15 0 2 Z 2 W 422 6 2 2 Z 2 W 422 10 1 2 Z 2 W 233 15 0 2 Z 2 W 1266 3 2 2 Z 2 W 466 10 1 2 Z 2 W 610 6 2 Misto 312 15 0 Misto 1046 6 2 141 Alessandro Ballestrero I 1 20 The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 55

PHASE Monte Carlo - Amplitude Are the groups with the same number of diagrams (e. g. 422) identical? Not really but can be programmed at the same time We are left with: 202 233 312 422 466 610 Simple arithmetics: 202=101 x 2 233=211 without hbb +22 312=101+211 466=233 x 2 610=211 x 2 +188 hbb 1046=312 x 2 + 422 1046 1266 422=211 x 2 1266 =422 x 3 cxchange of identical particles Only 101 211 22 94 independent diagrams Further simplification: subdiagrams But the combinatorics is complicated Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 56

PHASE Monte Carlo - Integration Several studies and tests Two main strategies are normally used: Adaptive - Not sufficient when one has completely orthogonal peaking structures (e. g. annihilation vs fusion vs tt) Multichannel - hundreds of channels (even one per diagram !) - peaking structure of propagators What if not all propagators can be resonant at the same time? Cuts might give inefficiency Resonances can reproduce badly long non resonant parts - Adaptive and/or weight of the various channels from the importance of single diagrams Problems with gauge cancellations of orders of magnitude among different feynman diagrams Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 57

PHASE Monte Carlo - Integration PHASE combines in a new way the two strategies. With adaptive calculations only few phase spaces (channels) for completely different structures are needed For every process the possible channels to be used are established, weights determined in thermalization and independent runs for every channel are performed Different mappings (up to 5) on the same variable of every phase space and a careful treatment of exchange of identical particles are employed Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 58

PHASE Monte Carlo - Generation One shot a la WPHACT One shot : Unweighted event generation of all processes (several hundreds) or any subset in a single run Interface with Les Houches Protocol to be used in a full experimental simulation procedure Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 59

Boson Fusion and Higgs Even if difficult define Boson scattering, PHASE can be used to compute and simulate possible consequences of EWSB in complete processes "dominated" by Boson fusion and Higgs production in the same channel in presence of complete irreducible background Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 60

Boson Fusion and Higgs peak and evident difference between normal SM Higgs scenarios and unexpected ones for high MWW Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 61

Boson Fusion and Higgs differences between different scenarios also at low MWW with much more statistics Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 62

Boson Fusion and Higgs difference between light higgs and no Higgs (m. H -> ) at high MWW Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 63

Boson Fusion and Higgs One can distinguish the contributions coming from different polarizations also for off shell W's, using For m. H -> LL dominates at high MWW Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 64

Boson Fusion and Higgs LL dominates also for light higgs at high MWW Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 65

Boson Fusion and Higgs 1 < η(d) < 5. 5 -1 > η(u) > -5. 5 E(u, d, c, s, μ) > 20 Ge. V Pt(u, d, c, s, μ) > 10 Ge. V 70< M(sc, μν) < 90 pt. W cut : m. H = 120 Ge. V pt. W > MW With LL and pt cut (as needed by EVBA) one looses a lot in cross section Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 66

Conclusions We have a lot of expectations from LHC Electroweak Physics will take part in many interesting physics problems Only a cooperation among the different areas and method will allow to exploit all potentialities of LHC A lot of challenging work is ahead of you Have fun ! Alessandro Ballestrero The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 67