The Search for the Higgs at the Fermilab Tevatron: Run 2 Higgs Gordon Watts University of Washington, Seattle May 10, 2001

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, The Run 2b Series UW is going to collaborate with D0 in building the inner most two layers of Si for the Run 2b detector Series of talks on that topic Archived on the Web: Tianchi’s excellent talks on construction, operation, and history of Si Vertex Detectors So Far:

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, The Standard Model Fundamental particles 3 families of fundamental fermions quarks leptons q = 0 q = -1 q = 2/3 q = -1/3 e   udud everyday matter Color Charge (3) cscs tbtb Electric Charge u u d proton All Seen,  most recent discovery

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Force Mediators W ±, Z 0 Weak Force  E&M Force gluon Strong Force (8) The g and the gluon are massless. W±W± Z0Z ± GeV/c ± GeV/c 2 LEPII & TeV Measurments Where does this mass come from?

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Boson Mass Initially Massless (Gauge Bosons) Quantum Corrections do generate some mass + +etc. Goldstone Bosons BUT Predicted Mass of the Z is of MeV order!

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Generating Mass Two common ways to generate mass in the SM Strong-Interactions between new fermions Adds terms to the correct calculation Considered less likely Weakly Interacting, self coupling scalar field The Standard Model incorporates the second The minimum additions Doublet of two scalars Vacuum expectation energy – key contribution to W,Z Mass calculations One degree of freedom left over The M Z is now very close (91 GeV/c 2 ) The Higgs M H is the free parameter

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Current Indirect Results The Higgs Mass indirectly affects the measured top and W masses CERN EWWG Even without discovery we know quite a bit about the Higgs H W WW “Radiative Corrections” CDF (GeV/c 2 ) D0 (GeV/c 2 ) MWMW ± ± MtMt ± ± 7.1 With LEP,  W = 34 MeV/c 2

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Direct Searches Discovery only when direct evidence seen Search Strategy depends on Higgs Mass Decay products depend upon the mass Collider Environment Background production! Production channel will determine background Determines backgrounds

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, SM Higgs Decay Excluded by LEP Know Higgs Mass Know Branching Ratios Character of decay is changing rapidly in Tevatron’s Search Region

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, SM Higgs Decay Modes M H = 130 GeV/c 2 M H = 110 GeV/c 2 Topology of decay is changing rapidly Higgs/SUSY Working group Report

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, At LEP Production e + e -  HZ e + e -  WW e e  H e e The L3 events we are waiting on… Search Channels Defined by the Z decay 4 jet (qqbb),     bb, e + e - bb, etc. In their mass region, H  bb almost 80%. Backgrounds Detector backgrounds, QCD production, l + l - qq, qq 

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, LEP Direct Search Results No Discovery But tantalizing hints! No Discovery But tantalizing hints!  Lower limit is GeV/c 2 Combined LEP Result Excess of 3  ALEPH 4j, 2j+mE T, 2j2 l Excess: 3.9  xsec: to high by ~2  e + e -  HZ

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Direct Searches at the TeV QCD 2j background Associated HW, HZ production Light Higgs Heavier Higgs W*W (SM) Use gluon fusion! Search Strategy: bb decay: M H ~< 120 W * W decay: M H ~> 130 SM Higgs Production

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Background Comparison M H (GeV/c2) ggWH+ZH Events in one fb -1 Light Higgs gg  H  bb 2 jet topology Swamped by QCD di-jet background! ZH,WH  llbb, bb, l bb, jjbb BackgroundsEvents WZ+ZZ4400 Wbb+Zbb14000 tt7500 WW10400 QCD 4-jet background will make jjbb difficult! Heavy Higgs W*W 2 lepton & mE T, lepton & mE T & 2 jet, 4 jet lepton & mE T & 2 jet has large ttbar, WZj

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, The Analysis MC Signal & Background Raw Data (light Higgs) Trigger Isolated Lepton Event Selection High P T Lepton, W B Jet ID Low & High Quality JJ Mass Remove QCD BG Data JJ Mass Plot ZH,WH  llbb, bb, l bb, jjbb WZ+ZZ  lljj tt  l bbqq Wbb+Zbb  l bb, llbb QCD bb  bbl (fake or b) JJ Mass Plot Same Process Compare with statistical tools, look for the mass bump, mass windows, etc.

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Run 2 at the Tevatron Energy now at  s 1.98 TeV 20% Increase in associated H production Larger pbar bunches x10 Larger Instantaneous Luminosity New Tracking, EM ID, readout New Tracking, EM ID, readout

Run 2 has started… (March 1 st, 2001) Collisions!

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Run 2: Detector Upgrades Both CDF & D0 have had extensive upgrades Quick Scan of the final states –B-quark tagging Increased coverage, layers of Si –2jet mass resolution Preshower, tracking, larger samples for jet energy calibration –Lepton ID Increased coverage –Missing E T No large improvements expected What can you Expect?

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Current Upgrade Status At the TeV Run 2 has started –Detectors are mechanically complete –Still installing and building electronics –Had a store of 36x36 (bunches). Final configuration. We have seen tracks! –Focus is now on improving the luminosity Radiation Losses At D0 several weeks ago

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Tracks! Si Only xy view Andy Haas Elastic Tracker Tracks whole detector at once 20% of our Si tracker cabled

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Combined Track Run Event First 36x36 Store Silicon Tracker Fiber Tracker

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Run 2 Predictions Predictions from a series of Run 2 workshops –EW, Top, Higgs/SUSY –Work of almost 100 people Monte Carlo’s used were not Run 2 detector simulators –Parameterized MC Next Task for CDF & D0 –Bring up experiments –Calibrate detector simulations with real data –Start searches Repeat efficiency & acceptance studies Invent new techniques! –Higgs/SUSY was optimistic already

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Run 2 Predictions 1.Detector efficiencies were extrapolated from Run 1 –Increased detector coverage was accounted for –3d tracking where we once had 2d (b-tagging) –Average Calorimeter/jet resolution for the two detectors (D0 is better) –Some assumptions are optimistic (jj resolution). No careful accounting for Multiple Interactions 2.Calculate efficiencies, acceptances –Luminosity required for discovery, 95% CL limit, etc.

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Jet-Jet Resolution Crucial for Light Higgs Discovery Higgs/SUSY Report Better Energy Scale Better Jet Algorithms  corrections A lot of work to do…

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, B Jet Tagging Displaced tracks are most powerful indicator Use likelihood and NN to combine other event features Jet P T Track charge/multiplicity Width Relative P T ’s/SLT Secondary Primary

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, B Tagging Recent BID review: Got tagging rate Background rate needs work

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Backgrounds Effort underway to calculate background rates to NLO Ellis, Cambel, Veseli hep-ph/ No QCD background No detector effect

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, SM By Channel Two Search Stradegies Put it together

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, SM Higgs Search (2003) (2006) Does not include ttH. The two experiments combined

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Detector Effects Achieving this will require a long-term effort Accelerator will change over the course of time Dead Silicon (radiation damage) Large effort underway to replace Consequences: 3.5 fb -1 8 fb fb fb -1 L1 & L2 will die Due to construction, and length of shutdown, faster/cheaper to replace whole detector!

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Instantaneous Luminosity Steady increase in delivered luminosity Instantaneous luminosity increases Tevatron Collides bunches Number of minimum bias events Can separate in z Increase bunch size Increase # of bunches

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Multiple Interactions Tevatron Collides bunches 1 Hard Scatter (Higgs production) Number of minimum bias events Can separate in z Beam Tilt in Z LHC Can simulate a displaced vertex! 3D Tracking Confusion in the tracker, trigger Better Tracking (pitch, etc.) 5E32

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Conclusions The Higgs Search is a long term one –It will take us 2 years to rule out M H = 115 GeV/c 2 at 95% CL. –5  discover of 115 GeV/c2 is just within our reach, according to study Will have things to say about MSSM –Light sparticle searches –Indirect measurements Pushing edge of promised luminosity –Will press for more luminosity –Will look for improved experimental techniques! First Conference Results: Spring 2002

Higgs in Run 2 at the Tevatron Gordon Watts University of Washington, Seattle May 10, Run 2 Indirect Results With 2 fb -1 of data (~2 years)  M W ~ 40 MeV/c 2  M t ~ 2.5 GeV/c 2 (per experiment)  M H ~ 80% M H Top will not by statistics limited Large Top dilepton samples Large W statistics Split W samples to study systematics Better detectors -> better energy scale measurement 2-3 Years (continuous)