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

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 2 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 the 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, 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. Moreover we cannot exclude new phenomena that we do not expect

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 3 EW and QCD Strong interactions will be dominating: α S ten times bigger than α em 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: It is a strong process LHC is an hadronic collider. (x 1 x ) 90% 10% but....

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

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

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 6 EW and QCD A= g V g A /(g V 2 + g A 2 ) = asimmetry right left Data fitted : The Z parameters - lineshape and lepton asymmetry at LEP: m Z Γ Z σ h R l and A l FB - A e and A τ from τ polarization at LEP - A l from polarised left-right asymmetry by SLD - Heavy quark (b and c) measurementes at LEP and SLD: R b R c A b FB A c FB A b A c - sin 2 θ l eff from quark forward-backward asymmetry at LEP W mass m W at LEP and Tevatron Top mass m T at Tevatron sin 2 θ W from νN scattering data by the NuTeV experiment Input parameters for the calculations : α (m Z ) m Z G μ α S (m Z ) m t m h ( for the corrections ) Parameters of the fit: m Z m t m h α S (m Z ) and Δα h (5) (m Z ) (light quark contribution to running of alfa)

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 7 EW and QCD 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 EW corrections to QCD observables have started to appear Maina S. Moretti Ross...

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 8 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

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

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

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 11 EW logs : 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..... In the following I will mainly discuss the physics of vector bosons (W,Z) production and scattering why ew corrections can give important enhancements at high energies ? Sudakov logs corrections appear, which become important for s >> M W 2 Many NLO EW calculations have been performed, and NLO MC's start to appear One must however realize that At LHC they are of the order

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 12 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

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

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

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 15 Status of inputs WC2004: m t =174.3 ±5.1(exp) GeV/c 2 m W = ±0.034(exp) GeV/c 2 m Z = ±0.0021(exp) GeV/c 2 Z = ±0.0023(exp) GeV Z = ±0.0023(exp) GeV direct indirect EXCLUDED SM predictions from ZFITTER and TOPAZ0 programs Direct and indirect data favour a light Higgs ! W mass measurement

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 16 ( m H /m H 25%) Using had = Thanks to M.Grunewald direct Perspective at the LHC m W =15 MeV; m t =1 GeV m W =15 MeV; m t =1 GeV (world combined will look better than these ! – Tevatron run II, LEP2) (current central values assumed) SM constraints on m H : Chances of ruling out the SM ? EXCLUDED W mass measurement m W =30 MeV After LEP and Tevatron m W =30 MeV it will probably be possible to reach it will probably be possible to reach m W =15 MeV m W =15 MeV in the low lumi phase ! in the low lumi phase !

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

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 18 W production 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). 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

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 19 Famous example: Ew corrections to four fermion processes at e+ e- computed in double pole approximation W production Pole approximation LPA When one has resonant diagrams e.g. one can make an expansion of the complete amplitude around the complex poles retaining only leading order (residue at the poles) p 2 – M W 2 + i Г M W 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 forNLO corrections

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

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

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 22 W production Complete ew corrections O(α) Dittmaier Kramers single Z p p Z l + l - ZGRAD2 Baur Hollikl Wackeroth... single W p p W l ν O(α) parton cross section contain mass singuraties α ln(m q ) 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%)

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

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

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 25 Two boson production Vector boson pair production: test for non abelian structure of SM. New physics at energies much larger than those tested at LEP2 could modify these interactions. Effects of anomalous couplings will eventually be measured at LHC Eg. chargino neutralino gold plated signal for Susy 3 charged leptons + missing p T Background to new physics: ) Full ME's and O(α S ) 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%

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 26 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/M W ) neglecting logs of other invariants ( valid for, at large angles with respect to the beam ) and non factorizable corrections. 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 Mc has full processes and at Born level (IBA) Corrections in (single or double) Pole approximations We are still far from complete ew corrections for four fermions but in this case they are probably not needed

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

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

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

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

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 31 Boson Boson scattering and unitarity If Higgs does not exist or its mass too large, new physics must appear at TeV scale (LHC) A signal for this is an unexpected growth with energy of WW (Boson 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 Boson scattering. These are connected to new mechanisms to restore unitarity Can Boson 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+ W- which contain contributions of the type

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

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

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

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 35 is a function of q 1 and q 2. (spacelike) EVBA : extrapolation and deconvolution ? -1 n+1 q 2 off shell 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.

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 36 Finding information on boson 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. EVBA : extrapolation and deconvolution ? The energy of the WW scattering is determined by the invariant WW mass

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 37 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 GeV

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 38 Boson 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 Boson Scattering studies.

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

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

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 41 no higgs unitary σ (pb) ratio ww / all All diagrams1.86 E WW fusion diagrams 6.67 m_h=200 m WW >300 unitary σ (pb) ratio ww / all All diagrams8.50 E WW fusion diagrams 6.50 no higgs feynman σ (pb) ratio ww / all All diagrams1.86 E-2 13 WW fusion diagrams m_h=200 m WW >300 feynman σ (pb) ratio ww / all All diagrams8.50 E-3 26 WW fusion diagrams Boson Boson Scattering and Gauge Invariance Distributions show huge interference effect which are not constant: they depend very much on the value of the variable Previous results are confirmed by PP-> u s -> d c W + W - (on shell W's) Feynman gauge has still big cancellations but about a factor 30 less than unitary! Is it possible to find regions with low interference and use it to define WW scattering signal?

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 42 Boson Boson Scattering and Gauge Invariance pp us dc W + W - all diagrams unitary WW fusion ratio unitary feynman WW fusion ratio feynman NO HIGGS ratio = WW fusion / all

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 43 Boson Boson Scattering and Gauge Invariance pp us dc W + W - all diagrams unitary WW fusion feynman WW fusionratio feynman NO HIGGS ratio unitary

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

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 45 Boson Boson Scattering and Gauge Invariance unitary WW fusion feynman WW fusion ratio unitary ratio feynman pp us dc W + W - all diagrams t1t1 t2t2 t2t2 t1t1

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 46 Boson Boson Scattering and Gauge Invariance no cut M WW > 1000 GeV a cut on M WW does not change qualitatively but worsen the ratios t1t1 t2t2 ratio unitary ratio feynman

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

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 48 Useful also for comparison with different approach The processes we have considered involve in reality 6 fermion final states PHASE Monte Carlo - Purpose For them so far we have: We aim at a complete (all processes and all diagrams) and dedicated MC Full generation and simulation with high efficiency Interface to detector simulations 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 & MADGRAPH & MADEVENT, O'MEGA & WHIZARD, PHEGAS & HELAC ] 'generic' -> 'dedicated' is not a trivial step Non irreducible backgrounds by other MC 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

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 49 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 2q as All processes of the type PHASE Monte Carlo - Processes

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

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 51 Process Initial state multipl. Boson Boson scattering subprocess 7 diag 7 diag 4 diag 4 diag Total Number of Diagrams 2x422 2x 2x 2x 2x 2 1x 1x 2 W 2 Z PHASE Monte Carlo - Processes

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 52 Process Initial state multip. Boson Boson scattering subprocess 7 diag 7 diag 4 diag 4 diag Total Number of Diagrams 2x312 2xx 2 x 2xx 2xx 2x 2xx 2xx 2xx 2x 2xx 2xx 2xx 2xx 2 Mixed : 4 W + 2W2Z PHASE Monte Carlo - Processes

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero W Z2W Misto Misto Z2W Z2W Z2W Z2W Z2W Z2W Z2W Z2W Z2W Z2W Z2W Z2W Initial mult. 1Initial mult. 2 Number of processes Diagram number Type Outgoing particles how may processes and diagrams? 161 processes have different matrix elements processes which differ at least for pdf: 141 x = 302 x 4 (CC +Fam)= 1208 This only for em 6 PHASE Monte Carlo - Processes

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 54 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?

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 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...

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 56 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 : Simple arithmetics: 202=101 x 2 233=211 without hbb = =211 x 2 466=233 x 2 610=211 x hbb 1046=312 x =422 x 3 Only independent diagrams Further simplification: subdiagrams PHASE Monte Carlo - Amplitude cxchange of identical particles But the combinatorics is complicated

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 57 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

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 58. 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 PHASE Monte Carlo - Integration PHASE combines in a new way the two strategies

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

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

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

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

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

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 64 Boson 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 M WW

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

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 66 1 η(u) > -5.5 E(u,d,c,s,μ) > 20 GeV P t (u,d,c,s,μ) > 10 GeV 70< M(sc, μν) < 90 m H = 120 GeV Boson Boson Fusion and Higgs ptW cut : pt W > M W With LL and pt cut (as needed by EVBA) one looses a lot in cross section

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The Physic of LHC - Italo-Hellenic School – Lecce – May 2004 Alessandro Ballestrero 67 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 !

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