Searches for Non-SM Higgs at the Tevatron

Thomas WrightUniversity of Michigan

on behalf of the CDF and DØ Collaborations

XLIIIth Rencontres de MoriondQCD and High Energy Interactions

March 8-15, 2008

• This talk: neutral MSSM Higgs searches

• More exotic Higgs to follow (M. Mulhearn)

2Higgs 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 - “tan”– 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– tan : 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 tan near 1, h is SM-like and light – SM Higgs limits apply

• Larger tan and light mA shows more interesting behavior

3Higgs at High tan

b

0

b

b

0Processes involving bottom quarks (down-type) can be enhanced (goes like tan2)

Boost from femtobarns to picobarns

Could be observable at Tevatron!

via top loop

0 = h/H/A

here, H = A or h/HH = SM Higgs

4Higgs at High tan

• Neutral sector simplifies at high tan

• A and h/H become degenerate

• Other scalar SM-like, low cross section

• Only need to search for a single mass peak ()

• For the A and its twin h/H, at high tan decays into bb (90%) and (10%) dominate

• So, for example, won’t see enhancement in HWW* channel

• CDF and DØ are searching in both of these decay modes

5The Channel• Unique final state – can look for inclusive production• Main backgrounds: Z , W+jets, dibosons

• One tau decays leptonically: e/ (CDF) or (DØ) (plus ’s)– pT > 10 GeV/c (CDF), 15 GeV/c (DØ)

• Other tau hadronic (both) (and )

– One or three tracks (qtrk = ±1), opposite to lepton

– CDF : isolation 30°, shrinking cone (10° 3°)– DØ : three types (±, ±0, 3-prong), NN score

• No electron veto (allows e)– pT > 15 GeV/c (1-prong), 20 GeV/c (3-prong)

• Also e (CDF), pT > 10, 6 GeV/c

• Reject non- background– Lepton and missing energy

inconsistent with W– HT cut (CDF) or kinematic NN (DØ)

h ID

cone

isolation

Multiple neutrinos can’t reconstruct mass very well

6CDF Results

Last year at this time, CDF had a >2 excess around 160 GeV/c2 (<2 over all m)

mvis (GeV/c2)

mvis (GeV/c2)

• Updated Fall 2007 with an additional 0.8 fb-1 of data

• No excess in e/ + had channel after update

Moriond 2007, CDF 1 fb-1

7CDF Results

mvis (GeV/c2)

mvis (GeV/c2)

No apparent excess in e channel either

Set x BR limits

8DØ 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 x BR limits

9MSSM Interpretation

Interpret x BR limits as limits on tan vs mA in MSSM benchmark scenarios• More data and analysis improvements on the way

• Project missing momentum onto axes for boosted Higgs (improve m)

• Split into b-tagged and untagged samples (already demonstrated by DØ)

• Updated results from DØ in and b channels coming soon!

DØ b 340 pb-1

10The bb Channel

• 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

Dawson, Jackson, Reina, Wackeroth hep-ph/0603112

b quark pT >20 GeV/c, ||<2

b

b

0

b

0too much background

with bb, 3b total

11B-Jet Identification

• CDF : displaced vertices with Lxy/ cut

• Vertex mass separation

• DØ : combine vertex properties and displaced track info with NN

• Tag to beyond 2

CDF

DØ

12DØ 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 x BR

mH = 120

13CDF 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

14CDF 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

15CDF 3b Results

• No significant excess observed

• Set limits on x BR

• Background systematics limitingimprovement at low mH• Focus of the next round

16MSSM Interpretation

• Interpret in MSSM scenarios

• Include effect of Higgs width(~20% for tan = 100)

• Lose sensitivity (lower S/B)

• Lowers event yield

• Best limits obtained in scenarios with < 0 (loop enhancements)

17Summary

• 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 m and S/B with b-tagging– 3b: background shape systematics (CDF)

• DØ updates on all three channels (, b, 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 tan in the 20’s with full Run II samples

• Or, with the right mA and tan,make a discovery!

Backup Material

19Charged Higgs

• 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)

• CDF : use dilepton, l+jets (single and double-tagged), and lepton+tau ’s

• Consider H+ , cs, t*b, W+bb• Map out allowed and excluded

regions in mH+ vs tan using CPsuperH and CDF simulation to predict effects on top ’s

20CDF Projections