Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 1 Vector Boson Fusion Produced Higgs Decays to  Jessica Leonard University of Wisconsin - Madison Preliminary Examination

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 2 OutlineOutline Motivation for Higgs Higgs Physics Higgs Signals Large Hadron Collider Compact Muon Solenoid Detector Monte Carlo Event Selection Simulation Results Future Plans

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 3 Standard Model Matter particles Leptons Quarks Force carriers Photons Gluons Gauge bosons

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 4 The Higgs Particle Standard Model hinges on one particle we haven’t seen yet: the Higgs boson! What does the Higgs do? Breaks symmetry between electromagnetic and weak forces Gives mass to W, Z bosons Coupling to other particles determine their masses: stronger coupling = higher mass Also gives mass to itself (self-couples) In other words, the Standard Model needs the Higgs!

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 5 Expected Higgs Mass Precision electroweak measurements predict a range for the Higgs mass Large Electron- Positron Collider (LEP) at CERN ( GeV) searched for Higgs and set a mass limit of ~ 115 GeV LEP excluded

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 6 Improved Higgs Constraints Tevatron collides protons with anti-protons at a center of mass energy of 1.96 TeV

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 7 Proton-proton Interactions at the LHC Luminosity L = particle flux/time Interaction rate Cross section  = “effective” area of interacting particles

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 8 General Higgs Production Gluon-gluon fusion high rate, but high QCD background Vector boson fusion lower rate, but lower background

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 9 Higgs decays Low Higgs mass: most prominent signal below ~100 GeV,  is second  jets easier to identify than b jets Higher Higgs mass: WW most prominent decay above ~200 GeV ZZ second

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 10 Vector Boson Fusion to  VBF Relatively high rate Identification of Higgs production via quark products in final state H->  Relatively high rate for low-mass Higgs Distinct signal qqH->  : Good potential for discovery!

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 11 Finding VBF Higgs->  Example Feynman diagram: Detector sees leptons and hadrons Electron seen as ECAL energy + track Pion seen as HCAL energy + track Tag quarks become jets -- see next slide

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 12 Hadronization and Jets Colored partons produced in hard scatter → “Parton level” Colorless hadrons form through fragmentation → “Hadron level” Collimated “spray” of real particles → Jets Particle showers observed as tracks and energy deposits in detectors → “Detector level” ProducedObserved

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam kilometer ring near Geneva, Switzerland (formerly the LEP ring) Proton-proton collisions Center of mass energy 14 TeV Design luminosity cm -2 s -1 Physics in 2008 Large Hadron Collider

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 14 LHC Magnets Superconducting NbTi magnets require T = 1.9K 1232 dipoles bend proton beam around ring, B = 8T Quadrupoles focus beam

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 15 LHC Startup Plan Stage 1 Initial commissioning 43x43  156x156, 3x10 10 /bunch L=3x x10 31 Stage 2 75 ns operation 936x936, 3-4x10 10 /bunch L= x > ~1fb -1 Stage 3 25 ns operation 2808x2808,3-5x10 10 /bunch L=7x x >~10fb -1 Stage 4 25 ns operation Push to nominal per bunch L= > ~100fb -1 /yr Shutdown Long Shutdown Year one (+) operation Lower intensity/luminosity: Event pileup Electron cloud effects Phase 1 collimators Equipment restrictions Partial Beam Dump 75 ns. bunch spacing (pileup) Relaxed squeeze Phase 2 collimation Full Beam Dump Scrubbed Full Squeeze Starts in 2008

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 16 Experiments at the LHC ATLAS and CMS : pp, general purpose

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 17 Compact Muon Solenoid (CMS) MUON BARREL CALORIMETERS Pixels Silicon Microstrips 210 m 2 of silicon sensors 9.6M channels ECAL 76k scintillating PbWO4 crystals Cathode Strip Chambers (CSC) Resistive Plate Chambers (RPC) Drift Tube Chambers (DT) Resistive Plate Chambers (RPC) Superconducting Coil, 4 Tesla IRON YOKE TRACKER MUON ENDCAPS HCAL Plastic scintillator/brass sandwich Weight: 12,500 T Diameter: 15.0 m Length: 21.5 m

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 18 Current CMS Progress Endcap disk -- Wisconsin!

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 19 Seeing Particles in CMS Lead Tungstate Brass/Scintillator

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 20 TrackerTracker Silicon strip detector used in barrel and endcaps Silicon pixel detectors used closest to the interaction region Tracker coverage extends to |  |<2.5, with maximum analyzing power in |  |<1.6

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 21 Electromagnetic Calorimeter ECAL measures e/  energy and position to |  | < 3 ~76,000 lead tungstate (PbWO 4 ) crystals High density Small Moliere radius (2.19 cm) compares to 2.2 cm crystal size Resolution:

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 22 Hadronic Calorimeter HCAL samples showers to measure their energy/position HB/HE -- barrel/endcap region Brass/scintillator layers Eta coverage |  | < 3 Resolution: HF -- forward region Steel plates/quartz fibers Eta coverage to  5 Resolution:

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 23 Muon System Muon chambers identify muons and provide position information for track matching. Drift tube chambers max area 4m x 2.5m cover barrel to |  |=1.3 Cathode strip chambers in endcaps use wires and strips to measure r and , respectively. Coverage |  |=0.9 to 2.4. Resistive plate chambers capture avalanche charge on metal strips. Coverage |  |<2.1

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 24 TriggerTrigger

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 25 Level-1 Trigger Identifies possible leptons,  -jets, etc. Implemented in hardware Project to emulate L1 in software for validation Reduces rate from 40 MHz to up to 100 kHz Processes each event in 3  s

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 26 Calorimeter Trigger Geometry

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 27 Calorimeter Trig. Algorithms Electron (Hit Tower + Max) 2-tower  E T + Hit tower H/E Hit tower 2x5-crystal strips >90% E T in 5x5 (Fine Grain) Isolated Electron (3x3 Tower) Quiet neighbors: all towers pass Fine Grain & H/E One group of 5 EM E T < Thr. Jet or  E T 12x12 trig. tower  E T sliding in 4x4 steps w/central 4x4 E T > others  : isolated narrow energy deposits Energy spread outside  veto pattern sets veto Jet    if all 9 4x4 region  vetoes off

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 28 Event Reconstruction Reconstruction done using High-Level Trigger (HLT) Offline -- uses a computer farm Reduces rate from Level-1 value of up to 100 kHz to final value of ~100 Hz Slower, but determines energies to high precision

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 29 Jet Reconstruction Example: Cone Algorithm Procedure Construct seeds (starting positions for cone) Move cone around until E T in cone is maximized Determine the merging of overlapping cones R

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 30 Electron Reconstruction Create “super-clusters” from clusters of energy deposits using Level-1 EM calorimeter information Must be in area specified by Level-1 trigger Must have E T greater than some threshold Match super-clusters to hits in pixel detector Electrons create a hit Photons do not! Combine with full tracking information Track seeded with pixel hit Final cuts made to isolate electrons Pixels Tracker Strips ETET pTpT E T /p T cut

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 31 Tau Reconstruction Reconstruct “tau jet” from calorimeter candidate Highest-p T track within cone of radius R m is leading signal track Tracks within signal cone (radius R s ) having same vertex assumed to come from  decay No other tracks from that vertex may be in cone of radius R i ECAL/HCAL information used to correct energy

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 32 Monte Carlos How do we know all our algorithms actually work? Simulate the entire event Run it through the actual reconstruction. We know what the “right” answer is, so we can tell how well our reconstruction algorithms work. Framework for reconstruction is CMS SoftWare (CMSSW) Physics Processes (PYTHIA) Detector Simulation (GEANT4) Electronics Simulation (CMSSW) Reconstruction (CMSSW) Physics Objects (CMSSW) Random numbers 4-vectors Hits Digis Clusters, Tracks Electrons, Muons,...

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 33 Monte Carlos (MCs) Parton Level Simulated by PYTHIA Hadron Level Model Fragmentation Model (PYTHIA) Detector Level Detector simulation based on GEANT Detector Simulation Parton Level Hadron Level

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 34 Lund String Fragmentation Used by PYTHIA to describe hadronization and jet formation. Color “string" stretched between q and q moving apart Confinement with linearly increasing potential (1GeV/fm) String breaks to form 2 color singlet strings, and so on., until only on mass-shell hadrons remain.

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 35 Z->  Backgrounds 2  + 2 jets Includes both QCD (  = 1615 fb) and EW (  = 299 fb) processes (for m H = 135 GeV,  Higgs = fb) Irreducible background produces same final state as signal

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 36 EW and QCD W+jets Backgrounds W + jets (  = x 10 3 fb) One jet fakes a , the others are identified as tag jets

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 37 Top Background -> WbWb (  = 86 x 10 3 fb) b decays fake tag jets

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 38 qqH->  Selection Strategy Level-1 Single isolated electron, single muon, OR e-  trigger HLT Single isolated electron, single muon, e-  OR  -  trigger VBF Cuts Require angular separation, invariant mass of forward jets consistent with vector boson fusion Transverse mass of lepton-missing E T system Cut to eliminate W peak

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 39 Event Selection Results Physics Technical Design Report analysis: Higgs signal generated with PYTHIA Backgrounds generated with several programs, including Alpgen and MadGraph Cut summary table:

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 40 Selection Details: p T Lepton p T > 15 GeV Used in electron reconstruction Also reduces QCD 2  background  -jet p T > 30 GeV Used in  reconstruction Also reduces QCD and EW 2  background

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 41 Angular Separation Require  > 4.2 Reduces top background Cutoff in QCD, W below 4 due to generation Require  < 2.2 Reduces QCD/EW irreducible and W+jet backgrounds

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 42 Invariant, Transverse Mass Require forward jet invariant mass > 1000 GeV Reduces top background Cutoffs at ~500 GeV due to generation Require lepton/missing energy transverse mass < 40 GeV Reduces W+jets background, as well as top background

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 43 Invariant Mass of  Pair After all cuts: Peak from QCD and EW production of Z clearly visible Peak from Higgs also visible!

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 44 Further cut optimization studies Plots using Wisconsin-generated Higgs events, m H = 130 GeV No background events yet Electron p T Forward Jets Invariant Mass GeV

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 45 ConclusionsConclusions Higgs discovery in this channel is possible! Higgs decay to  clear signal The tag jets improve identification of vector boson fusion with 30 fb -1, which we expect within a few years of turn-on Current analysis methods can reduce background enough to see Higgs signal In the meantime, I will be working on Wisconsin duties at CMS Regional Calorimeter Trigger Continue studies outlined in this talk

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 46 ExtrasExtras

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 47 SLAC Standard Model Chart

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 48 Higgs Physics More info on Why We Need the Higgs?? Talk about: Higgs required to give mass to W and Z, also couples with most other particles -- coupling strength determines masses of those particles

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 49 TriggerTrigger

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 50 Tau decay Require a “narrow” jet in the calorimetry. Require confirmation from the tracking, and isolation around the narrow jet.

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 51  decays in detector Higgs decays isotropically, so signature in general is in central detector (as opposed to forward)  -> W* + , then W* -> lepton + l OR W* -> u + dbar e.g., more hadronization possible (single- and triple-prong events) What do these look like in the detector? lepton + l : electron (ECAL energy + track) or muon (muon chamber energy + track) + missing energy hadrons : hadronic jet (HCAL energy + odd number of tracks), energy deposit must be small and contiguous - -> tagged as “  jet”

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 52 H->  final states and triggers Note: Here “jet” means energy deposit consistent with   ->jj (NOT actually a final state in PTDR study) L1: single or double  (93, 66 GeV) ??? HLT: double  ???  ->  j L1: single  HLT: single ,  +  jet  ->ej L1: single isolated e, e +  jet HLT: single isolated e, e +  jet

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 53 H->  ->l+ +single-prong event offline selection e and  candidates identified Additional electron requirements: E/p > 0.9 Tracker isolation Hottest HCAL tower Et < 2 GeV Highest-pt lepton candidate with pt > 15 GeV chosen Lepton track identifies the other tracks of interest: within  z = 0.2 cm at vertex

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 54 H->  ->l+ +single-prong event offline selection (cont.)  candidates identified; jet formed around each and passed through t-tagging requirements Require  -jet charge opposite lepton charge Hottest HCAL tower Et > 2 GeV if  coincides with electron candidate  -jet Et > 30 GeV

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 55 H->  ->l+ +single-prong event offline selection (cont.) Jets are the 2 highest-Et jets with Et > 40 GeV, not including e and  candidate Jets must be within |  | < 4.5, as well as having different signs in h Require  hj1j2 > 4.5,  fj1j2 1 TeV Require transverse mass of lepton-MisEt system < 40 GeV

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 56 H->  ->2 1-prong Backgrounds: ttbar, Drell-Yan Z/  *, W+jet, Wt, QCD multi-jet

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 57 H->  ->  +jet

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 58 H->  ->e+jet

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 59 Generic Z->  bg diagram

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 60 Back-up slides

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 61 Structure of the Proton Proton contains 3 valence quarks (uud) Many “sea” quark- antiquark pairs Gluons

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 62 Dipole Photo

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 63 Dipole Magnet Field Diagram Field Diagram

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 64 ATLASATLAS ATLAS info

Jessica Leonard, U. Wisconsin, February 15, 2007 Preliminary Exam - 65 ECAL crystal ECAL lead tungstate crystal