1 / 20

Searches for Non-SM Higgs at the Tevatron

Searches for Non-SM Higgs at the Tevatron. Thomas Wright University of Michigan on behalf of the CDF and DØ Collaborations. This talk: neutral MSSM Higgs searches More exotic Higgs to follow (M. Mulhearn). XLIII th Rencontres de Moriond QCD and High Energy Interactions March 8-15, 2008.

velvet
Télécharger la présentation

Searches for Non-SM Higgs at the 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. Searches for Non-SM Higgs at the Tevatron Thomas Wright University of Michigan on behalf of the CDF and DØ Collaborations This talk: neutral MSSM Higgs searches More exotic Higgs to follow (M. Mulhearn) XLIIIth Rencontres de Moriond QCD and High Energy Interactions March 8-15, 2008

  2. Higgs in the MSSM • In the standard model, one complex doublet = four scalar fields • Three turn into W/Z mass  one physical scalar • Minimal Supersymmetric Standard Model (MSSM) requires two doublets • One couples only to up-type fermions, the other only to down-type • Ratio of VEV’s - “tanb” • Eight scalar fields – three for W/Z mass = five physical scalars • Three neutral (h, H, A), two charged (H±) • Properties of the Higgs sector largely determined by two parameters: • mA : mass of pseudoscalar • tanb : ratio of VEV’s • Higher-order effects introduce other SUSY parameters(benchmark scenarios, see Carena et al., hep-ph/0511023) • Typically, mh < mA < mH , and mH± ~ mA • For tanb near 1, h is SM-like and light – SM Higgs limits apply • Larger tanb and light mA shows more interesting behavior

  3. Higgs at High tanb 0 b b 0 b Processes involving bottom quarks (down-type) can be enhanced (goes like tan2b) Boost from femtobarns to picobarns Could be observable at Tevatron! f0 = h/H/A via top loop H = SM Higgs here, H = A or h/H

  4. Higgs at High tanb Neutral sector simplifies at high tanb A and h/H become degenerate Other scalar SM-like, low cross section Only need to search for a single mass peak (f) • For the A and its twin h/H, at high tanb decays into bb (90%) and tt (10%) dominate • So, for example, won’t see enhancement in HWW* channel • CDF and DØ are searching in both of these decay modes

  5. The  Channel th ID t cone isolation • Unique final state – can look for inclusive f production • Main backgrounds: Z tt, W+jets, dibosons • One tau decays leptonically: e/m (CDF) or m (DØ) (plus n’s) • pT > 10 GeV/c (CDF), 15 GeV/c (DØ) • Other tau hadronic (both) (and nt) • One or three tracks (Sqtrk = ±1), opposite to lepton • CDF : isolation 30°, shrinking t cone (10° 3°) • DØ : three types (p±, p±p0, 3-prong), NN score • No electron veto (allows em) • pT > 15 GeV/c (1-prong), 20 GeV/c (3-prong) • Also tt em (CDF), pT > 10, 6 GeV/c • Reject non-tt background • Lepton and missing energyinconsistent with W • HT cut (CDF) or kinematic NN (DØ) Multiple neutrinos  can’t reconstruct tt mass very well

  6. CDF tt Results Moriond 2007, CDF 1 fb-1 mvis (GeV/c2) Last year at this time, CDF had a >2s excess around 160 GeV/c2 (<2s over all mf) Updated Fall 2007 with an additional 0.8 fb-1 of data No excess in e/m + thad channel after update mvis (GeV/c2)

  7. CDF tt Results No apparent excess in em channel either Set s x BR limits mvis (GeV/c2) mvis (GeV/c2)

  8. DØ tt Results Visible mass (like CDF) Just one input to search NN, along with lepton, tau kinematics Do not see any excess (as was the case last winter) Set s x BR limits

  9. MSSM Interpretation DØ btt 340 pb-1 Interpret s x BR limits as limits on tanb vs mA in MSSM benchmark scenarios More data and analysis improvements on the way Project missing momentum onto t axes for boosted Higgs (improve mtt) Split into b-tagged and untagged samples (already demonstrated by DØ) Updated results from DØ in tt and btt channels coming soon!

  10. The fbb Channel b quark pT >20 GeV/c, |h|<2 0 b b Dawson, Jackson, Reina, Wackeroth hep-ph/0603112 0 b • Inclusive H  bb is too hard due to QCD background • Require one additional bottom quark jet besides the two from Higgs decay • “3b” channel best compromise between signal and background rates too much background with fbb, 3b total

  11. B-Jet Identification CDF • CDF : displaced vertices with Lxy/s cut • Vertex mass separation • DØ : combine vertex properties and displaced track info with NN • Tag to h beyond 2 DØ

  12. DØ 3b Channel • Result with 0.9 fb-1 (2006), update coming soon! • Search uses invariant mass of the two leading jets m01 in triple-tagged events • Derive background shape from double-tagged sample • Correct for kinematic bias of third jet tag • Normalize background to data in sideband region, look inside the signal window • No excess observed, set limits on s x BR mH = 120

  13. CDF 3b Channel • New result for Moriond QCD 2008, using 1.9 fb-1 • Search in mass of two lead jets m12 • Backgrounds are events with two true b-tags, and a b/c/fake tag • Characteristic m12 spectra for each • Start from bb+jet sample (corrected double-tags), weight events by flavor hypothesis • Correct bbb and bcb shapes for double/triple-tag selection bias • Largest systematic error • Fit the observed m12 spectrum with the backgrounds and a Higgs shape

  14. CDF 3b Channel • Improve prediction of total background m12 using tag properties • Invariant mass of tracks in each vertex mj • m1+m2 : bbb+bbx / bcb+bqb • m3 : bbx / bbb+bcb+bqb • Unstack into 1D variable “xtags” for plotting/fitting • Fits are 2D – m12 vs xtags • Four backgrounds • Higgs signal template

  15. CDF 3b Results • No significant excess observed • Set limits on s x BR • Background systematics limitingimprovement at low mH • Focus of the next round

  16. MSSM Interpretation • Interpret in MSSM scenarios • Include effect of Higgs width(~20% for tanb = 100) • Lose sensitivity (lower S/B) • Lowers event yield • Best limits obtained in scenarios with m < 0 (loop enhancements)

  17. Summary • CDF and DØ are looking hard for neutral MSSM Higgs bosons • Lots of progress but no discovery as of yet • Techniques are well-advanced but still room for improvement • Taus: split samples to improve mtt and S/B with b-tagging • 3b: background shape systematics (CDF) • DØ updates on all three channels (tt, btt, 3b) coming soon • Combination of experiments/channels is planned • Results today use 1-2 fb-1, expect 5-6 by 2009 (7 by 2010?) • Could probe down to tanb in the 20’s with full Run II samples • Or, with the right mA and tanb,make a discovery!

  18. Backup Material

  19. Charged Higgs CDF : use dilepton, l+jets (single and double-tagged), and lepton+tau s’s Consider H+ tn, cs, t*b, W+bb Map out allowed and excluded regions in mH+ vs tanb using CPsuperH and CDF simulation to predict effects on top s’s • Search in top decays • t  H+b • DØ : ration of cross sections l+jets/dilepton • BR(t  H+b) < 0.35 @ 95% CL (for H+  cs)

  20. CDF tt Projections

More Related