H ->  introduction Satoru Uozumi Jan-9 th 2010 KNU/TAMU meeting Introduction for students - Photon signal - Higgs generation and decay Photon ID at CDF ….

Silicon Vertex Detector (precise position measurement) Tracking Chamber (momentum measurement) 1.4 Tesla Solenoidal magnet Calorimeter (Electromagnetic/Hadron) (energy measurement) Muon Detector (yellow & blue) Photon signal has no associated track (because of no electric charge) small and dense shower signal in electromagnetic calorimeter, similar with electron Intro – photon signal at CDF

– Hadronic part – Electromagnetic part (cell size ~ 20cm) for photon/electron energy measurement. Shower-max detector (CES) for shower position measurement. e/  Shower signal Intro - The CDF Calorimeter CES signal Track Photon Not photon

Sungwon Lee2003 CTEQ Summer School4 In principle, it’s the same also in CMS Photon candidates: isolated electromagnetic showers in the calorimeter, with no charged tracks pointing at them Identification of Photon Signal

However, photon-ID is more difficult in CMS… Simplest two-photon event at CDF (photon event is not always like such simple !) Simulated Higgs -> 2 photon event at CMS In CMS, there are more background tracks and clusters due to more QCD background and pile-up events (=multiple collisions at one bunch crossing). Clusters only in EM calorimeter No associated track to the clusters

CDF Photon ID for Higgs/exotic search “standard CDF photon ID” for Randall-Sundrum Graviton and H->  search (CDF 8858 etc.) Criteria is similar with electron selection, but without track.    00 EM Calorimeter Shower Maximum Detector Preshower Detector Main background : collimated photons from  0 decay in jet (in jet)

Neural Network approach for CDF Photon ID CDF 5791 … Electron/Photon ID with Neural Net JetNet package, S/B improved 1.9 -> 2.6 with Run I data CDF … multi-variable photon ID using TVMA package

Photon signal with e + e - conversion in CDF Photon signal is accessible also with electron data through conversion. However the conversion events are not used for exotic particles search with photons in CDF.

Sungwon Lee2003 CTEQ Summer School Photon Identification – learn from CDF Usually jet contains one or more  0 mesons which decay to photons –we are really interested in direct photons (from the hard scattering) –but what we usually have to settle for is isolated photons (a reasonable approximation) Isolation: require less than e.g. 2 GeV within e.g.  R = 0.4 cone This rejects most of the jet background, but leaves those cases where a single  0 or  meson carries most of the jet’s energy This happens perhaps 10 –3 of the time, but since the jet cross section is 10 3 times larger than the isolated photon cross section, we are still left with a signal to background of order 1:1 1. Conversion Probability:  ’s to convert in a preshower detector 2. Shower Profile: 2  ’s from  0 will produce EM showers with broader lateral and smaller longitudinal profiles 3. Reconstruction: requires good EM/angular resolution (fixed target) 1. Conversion Probability:  ’s to convert in a preshower detector 2. Shower Profile: 2  ’s from  0 will produce EM showers with broader lateral and smaller longitudinal profiles 3. Reconstruction: requires good EM/angular resolution (fixed target) There are a number of different technique to distinguish photons from  0 backgrounds. (see below) Additional issue for photon ID at LHC – pile-up of multiple collisions

Photon with e + e - conversion in CMS ? Due to tracker material: - photons have >50% probability to convert into e + e - pair - May give access to the photon signal ?

Production of SM Higgs Gluon fusion … dominant at LHC Vector boson fusion … 2 nd at LHC Two jets associated with Higgs qqbar -> WH, ZH ttH, bbH processes

SM Higgs decay LEPEWWG Summer2003 If the Higgs mass is in the SM preffereded region, many decay channels will be expected -> measurement of Higgs coupling can be measured to various particles 2 gamma decay is one of the important channel in this region

Possibility of Enhancement of non-SM H   decays H->  Branching Fraction Higgs Mass, GeV Standard Model no couplings to fermions (Fermiophobic Higgs) no couplings to down-type fermions in general we should be prepared for any H->  branching fraction ( up to 1.0 ) due to new physics S.Mrenna, J.Wells, Phys. Rev. D63, (2001) no couplings to top,bottom quarks

H ->  First analysis … inclusive search Easy - Just reconstruct masse from two photon candidates Sharp mass peak can be observed (thanks to good ECAL resolution) Background is large, though (S/B < a few%), Background can be estimated from mass sideband. Still important to understand components of backgrounds. CMS 14 TeV 1 fb-1 (signal scaled x10)

 +jet Reducible background jet+jet 58 % jet gluon 4.7 % jet quark 37.3 % mixture Partons  hadrons (« jets »)

Born(  QED 2 ) Bremsstrahlung (correction to Born) Box gg   (  s 2  QED 2 ) Irreducible background Calculation by Pythia (for ATLAS) M  (GeV)

Vector Boson Fusion analysis Study at ATLAS (LAPP-EXP ) Inclusive H -> gg analysis is simple, but BG is large If we focus on VBF process, S/B can be significantly improved - In addition to  signal, require two forward jets - Also require no 3 rd jet in central region

Prospect on photon-ID CDF photon-ID - “like electron without track” Difference at CMS : - finer ECAL granularity - Pile-up events - material budget At first, need to know what has been done for the CMS H->  analysis, then find out what we can do

Backups

Sungwon Lee2003 CTEQ Summer School21 Run 1  Run 2 subprocess  s Number of Events Run 2 Run 1 Increased reach for discovery physics at highest masses Huge statistics for precision physics at low mass scales Formerly rare processes become high statistics processes The TeVatron is a broad-band quark and gluon collider Extend the third orthogonal axis: the breadth of our capabilities

Sungwon Lee2003 CTEQ Summer School22 Signals Backgrounds    00 Photon candidates: isolated electromagnetic showers in the calorimeter, with no charged tracks pointing at them Identification of Photon Signals Central Calorimeter Shower Maximum Detector Preshower Detector CES has better separation, CPR better at high Et (Et>35) CDF/DØ uses two techniques for determination of photon signal; 1. EM Shower width 2. Conversion Probability CDF measures the transverse profile at start of shower (preshower detector) and at shower maximum DØ measured longitudinal shower development at start of shower CDF/DØ uses two techniques for determination of photon signal; 1. EM Shower width 2. Conversion Probability CDF measures the transverse profile at start of shower (preshower detector) and at shower maximum DØ measured longitudinal shower development at start of shower -- -Jet Jet-jet CES24±6%28±8%48±7% CPR29±23%40±28%30±23%

Sungwon Lee2003 CTEQ Summer School23 Photon Purity Estimators CDFCDF DØDØ DØ model longitudinal energy depositions of photon’s and jets and perform a statistical comparison to data using the discriminant variable to determine the photon purity. Each E T bin fitted as sum of: (a) = photons (b) = bgd w/o tracks (c) = bgd w/ tracks For every photon, using the conversion and profile info., CDF find the fraction of candidates with this info. (extracted signals statistically) E1: E in the 1st calo section

DiBoson Production For W  /Z  Photon Id is crucial: Main backgrounds:  0 →  jets faking photon Fake Rates: T =10 GeV 0.05% JetE T >25GeV Test Gauge Boson Self Interactions SM Higgs searches Resonance searches: Look for excess in kinematical distributions: E T (  ), 3body mass, lepton P T Complementarity with LEP experiments: Probing at higher √s W-  final state E T (  )>7 GeV  R( ,l)>0.7 |   |<1.1 Cal & Trk Iso    00 Pre-Shower Detector Shower Maximun Detector EM Calorimeter