1 / 20

Charged Higgs Results from Tevatron

Sudeshna Banerjee. Beijing. Fermilab, Chicago. Tata Institute of Fundamental Research. Mumbai, India. For CDF and D Ø Collaborations. ?. What are Doubly Charged Higgs How do we look for them at the Tevatron Did we find them What can we say about their properties from experimental data.

paiva
Download Presentation

Charged Higgs Results from Tevatron

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Sudeshna Banerjee Beijing Fermilab, Chicago Tata Institute of Fundamental Research Mumbai, India For CDF and DØ Collaborations ? • What are Doubly Charged Higgs • How do we look for them at the Tevatron • Did we find them • What can we say about their properties from experimental data Charged Higgs Results from Tevatron ICHEP04 Beijing, China Aug 16, 2004

  2. p p s =1.96 TeV t = 396 ns Luminosity: 4  1031 cm-2s-1 (2003) Projection: 8  1031 cm-2s-1 (2004) Fermilab Batavia, Illinois Chicago CDF DØ DØ DØ CDF Booster p Tevatron p p source Main Injector & Recycler REACHED 10

  3. Properties of Doubly Charged Higgs • Doubly Charged Higgs Bosons appear in several models • L-R Symmetric models, Little Higgs model, MSSM • Higgs fields can be represented as a triplet in L-R symmetric models (along with neutral and singly-charged Higgs) • L-handed and R-handed Higgs fields are possible • In L-R Symmetric models, the Higgs triplets are only one of the Higgs multiplets that break symmetry between L- and R- handed weak interactions at low energy. • SUSY L-R models suggest low mass for a Doubly Charged Higgs (~100 GeV)

  4. W-W Fusion : Pair Production : H++ _ _ _ H++ q q q W - + W W q W q H-- g */Z* q Small probability Dominant Production mode Cross section independent of Fermionic coupling |EW - 1| Is small, experimentally observed ++ H -- Production of H± ± Doubly-charged Higgs production cross section is enhanced substantially (~35%) due to NLO corrections. R-handed H++ cross section is smaller by a factor of ~2 due to different value of coupling of these particles to Z bosons. M. Spira & M. Mühlleitner, hep-ph/0305288

  5. _ + q H++ + - q g*/Z* H-- - Decay of H± ± A typical decay Experimental Signature ofH± ± decay (Yukawa coupling >10-7) A pair of like sign di-leptons Couplings like WWH, HHH, HHW and Hwith hadrons are possible but with very small coupling constants (not considered). Contamination from other Standard Model processes is low because of the requirement of two high pT leptons of same sign.

  6.   • Z e e • Z   • bb, t t, Z • Cosmic rays eliminated by demanding that the two muons originate at the beam line coincident in time with each other and with a p p collision. Possible Background Decay Channels Important modes are those which produce like sign leptons with charge misidentification, probable for high pT tracks one electron radiates a photon which then converts to e+e-, check for photon conversion vertices. semileptonic decays leptonic decays • WZ/ZZ • W + jets • Hadronic jets eliminated by demanding isolated muons.

  7. Search Strategy • Choose events triggered with two high pT dileptons. • electron – energetic EM cluster • muon – a high pTtrack matched with a stub in the muon counter + a MIP trace in the EM calorimeter • Make more stringent selection offline. • Generate signal events in different H±± mass bins covering the search region. • Generate Monte Carlo samples for different background decay channels. • Use the same selection criteria on experimental data, signal and background samples. • If after final selection and background subtraction an excess is seen in experimental data, a discovery is claimed. • If no excess is seen, a limit on H±± is calculated.

  8. H±± m mchannel (100 % BR assumed) • Total signal efficiency for the above selection = 47.5 % ± 2.5 % (not mass dependent) Search performed by DØ experiment 113 pb-1 integrated luminosity used Offline selection of events : Preselection • Two muons, matched to good tracks (pT> 15 GeV) Isolation • Calorimeter ET in outer cone around the muon trace should be small • pT of tracks around the muon track should be small Acolinearity • D < 2.51 (requirement for events with less than 3 muons) Like sign requirement • Two of the muons should have the same charge Signal Monte Carlo generation (PYTHIA 6.2) • Samples with H±± massranging from80 GeV to 200 GeV are generated in steps of 10 GeV All efficiencies derived from data

  9. m m Z events dominate 95 b b events b bevents dominate Effect of Selection criteria (DØ ) preselection preselection + like sign muon requirement 101 data events reduces after isolation cut

  10. Final Yield (DØ ) preselection + like sign requirement + isolation + acolinearity preselection isolation acolinearity like sign 9.4 8.5 7.5 6.5 Signal (mass = 100 GeV) 5254 ± 47 4113 ± 43 368 ± 14 1.5 ± 0.4 Total background 5168 4133 378 3 Data

  11. CL (signal) = CL (signal+background)/CL(background) 95% Limit on H± ± Mass (DØ ) Lower Mass Limit H±± (R) = 98.2 GeV H±± (L) = 118.4 GeV Limit calculation depends on mass distribution for signal and background and experimental mass resolution (MCLIMIT - T. Junk, Nucl. Instrum. Methods A 434, 435 (1999)) Systematic Uncertainties – MC (27%), theory (10%), Luminosity (6.5%), normalization (5%)

  12. Integrated luminosity used • e e 235 ± 13 pb-1 • e  242 ± 14 pb-1 •  240 ± 14 pb-1 Search forH± ± (CDF) H++Acceptance Search in all dilepton decay channals – e e, e ,  Acceptance = (Kinematic + geometric) x etrig eID Leptons are selected in the central hregion

  13. e e decay channel (CDF) Backgrounds : • Z e e, one electron radiates a photon which converts to e+e- • Hadronic jets • W + jet • WZ Expected Number Low Mass Region High Mass Region mee < 80 GeV mee > 80 GeV mH= 100 GeV +0.9 Total background1.1 ± 0.4 1.5 5.8 -0.6 Observed Events = 1

  14. High Mass Region Expected Number Low Mass Region mll< 80 GeV mll> 80 GeV mH= 100 GeV +0.5 0.8 ± 0.4 10.1 0.8 -0.4 0.4 ± 0.2 0.4 ± 0.2 5.0 Di-lepton mass distributions (CDF) Backgrounds : Hadromic jets, W+jet, WZ Total background ( ) Total Background (e ) Observed Events = 0

  15. Limit Calculation (CDF) No events are found in the high mass regions of e e, e ,  samples. Limit on Higgs mass is calculated using Bayesian method with flat prior for signal and Gaussian prior for background and acceptance uncertainties. (e e = 133 , e  = 115 ,  = 136) GeV (L)  H++ (  = 115) GeV H++ (R) 

  16. Summary of mass limits Promptly Decaying H±± DØ HL,R Mass limits submitted to Phys. Rev. Lett. in April 2004 ±± (hep-ex/0404015) CDF HL,R Mass limitssubmitted to Phy. Rev. Lett. in June 2004 ±± (hep-ex/0406073)

  17. , dE/dx  (charge)2 • Main process of energy loss is ionization e  Monte Carlo sample • Electrons –W Long Lived Doubly Charged Higgs (CDF) • No constraint on the lifetime ofH±± , can be long • Search for particles with ct > 3 m, no decay within the detector • They will behave like heavy stable particles, (muons but more ionising) Measurement of ionization – dE/dx measurement along the charged particle track in tracker and calorimeter. Background –Advantage is lack of Standard Model decays. Events expected fromhighly ionizing particles. • Muons –data from cosmic rays (pure muon sample) • Hadronic decays for tausfrom Monte Carlo sample • QCD contributioncalculated from experimental data

  18. Loose SearchTight Search Total Background< 10-5 10-6 Data Candidates 0 0 Long Lived Doubly Charged Higgs (CDF) 206 pb-1 integrated luminosity used Select events which have a good muon track with pT > 18 GeV. Require a second track with pT > 20 GeV offline. Loose cut : • Tracker dE/dx >35 ns Tight cut : • Tracker dE/dx >35 ns • Energy (EM) > 0.6 GeV • Energy (Had.) > 4 GeV Use loose cuts for setting mass limits And tight cuts for discovery. 100 GeV 10.2 6.6 mH Expected Number 2.4 130 GeV 3.2

  19. Mass Limit for Long Lived Higgs Bayesian upper limit onH±± crosssection Upper Limit on No. of Signal Events at 95% C.L. for 0 Observed Events Total H±± Acceptance x Integrated Luminosity H±± = For a H±± mass of 130 GeV H±± cross section is 0.057 ± 0.0066 ± 0.0030 Mass Limit for Quasi-Stable Doubly charged Higgs is 134 GeV

  20. Conclusions Tevatron Results • Prompt Decays • Limits on L-handed Higgs have gone up to ~ 130 GeV • Limits on R-handed Higgs have gone up to ~ 113 GeV • DØ plans to include e e and e  modes in future. • Long Lived Higgs • Limit on Higgs mass is 134 GeV • Both experiments will redo the analyses with much more luminosity as good data is being collected at a steady rate at the Tevatron. LEP Results • For both promptly decaying and long lived Higgs • Mass Limit ~ 100 GeV • Tevatron has improved the limits on masses ofH±± • There is scope for much more improvement in the coming years

More Related