# Presentation: 861909

## Standard Model Higgs at LHC

**Standard Model Higgs at LHC**

- Sridhara Dasu, University of Wisconsin, CMS Collaboration

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## The Large Hadron Collider

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## Status of ATLAS & CMS

**Status of ATLAS & CMS**

- After successful testing of the 4-T CMS magnet and some detector components, above ground, by measuring cosmic rays, CMS is being lowered at Point 5

- ATLAS is being built in place at Point 1 - many sub-detectors, including the inner ones are already installed.

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## SM Higgs Mass Constraints

- Direct Limit
- LEP-II: MH > 114.5 GeV (95% CL)
- Indirect Limit
- EW (LEP/SLD/Tevatron): MH < 166 GeV (95% CL)
- Theoretical Bound
- Higgs self-energy correction: MH < few hundred GeV beyond which Higgs is not a particle.
- LHC experiments were designed to look for SM like higgs with masses ranging from ~100 GeV through ~TeV
- Onus is upon LHC experimenters to design analyses to look for SM like higgs for masses above the current direct limit of 114 GeV
- Even in the region in disagreement with indirect limits.

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## SM Higgs mass constraints

**Indirect constraints from precision EW data **
**   ****M****H**** < 260 GeV at 95 %CL (2004)**
**   ****M****H**** < 186 GeV with Run-I/II prelim. (2005)**
**   ****M****H**** < 166 GeV (2006) **

**Theoretical bounds obtained as a ****function of the cut-off scale ****** by demanding that the Higgsself-coupling remains finite** **

**Direct limit from LEP: M****H**** > 114.4  GeV**

**SM Higgs mass constraints**

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## Higgs Production at LHC

**Higgs Production at LHC**

- Dominated by ggH
- qq qqH comparable at large MH
- Top and W,Z associated production have reduced backgrounds

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## Standard Model Higgs Decay

**Standard Model Higgs Decay**

- 115 < MH < 130 GeV
- Hbb dominates - however, to avoid backgrounds, use H
- MH > 130 GeV
- HWW*, HZZ*, HWW, HZZ (at least one lepton to avoid backgrounds)

- HWW(*)ll HZZ(*)4 leptons

- qqHWWljj qqHZZll  qqHZZll jj

- H

- qqH

- ttHWb Wb bb
- WHlbb

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## What’s New

- Will concentrate on CMS simulation results from CMS Physics TDR, V2, 2006
- Compare to ATLAS simulation results in summary
- Discovery potential for the Higgs boson using CMS is updated in comparison with Higgs Summary Note, CMS Note 2003 :
- Latest trigger table
- Background estimates from “data” and inclusion of experimental systematic errors
- Advanced generators for multi-jet events: ALPGEN, MadGraph, CompHEP, TopRex
- Almost all analyses use full G4 simulation data

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## HZZ(*)4l – The Golden Mode 

**Background: tt, ZZ, *****ll*****bb (“Zbb”)**
**Selections :**
** ****lepton isolation in tracker and calorimeter**
** ****lepton impact parameter, ********, ee vertex    **
** ****mass windows M****Z(*)****, M****H**

**H********ZZ********ee ******

**H********ZZ****(*********)********4*****l***** – The Golden Mode **

- All elements of the detector need to be in working order

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## New elements of analysis:
ZZ background: NLO k factor depends on m4l
background from side bands or from ZZ/Z;  (gg->ZZ is added as 20% of LO qq->ZZ,  no good generator yet) 

**New elements of analysis:**
**ZZ background: NLO k factor depends on m****4l**
**background from side bands or from ZZ/Z;  (gg->ZZ is added as 20% of LO qq->ZZ,  no good generator yet)**

***Signal and background at 5 sigma discovery***

**ee******

**ee******

**CMS**
**at 5******** sign.**

**CMS**
**at 5******** sign.**

**H********ZZ****(*********)********4*****l***

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## HZZ(*)4l

**~ 125 GeV**

**H********ZZ****(*********)********4*****l***

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## Inclusive H

***Went then from hybrid silicon + gas chamber tracker to ******all silicon tracker increasing material in front of calorimeter***

**CMS plot of the ECAL TDR time : December 1997**

**Inclusive ****H******

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

##  Conversion in Tracker

**CMS**

****** ****Conversion in Tracker**

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## Will new BGs degrade performance?

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## H Mass Plots

**barrel with good ********s**

**barrel with OK ********s**

**endcaps with good ********s**

**endcaps with OK ********s**

- 1 fb-1

- 1 fb-1

- 1 fb-1

- 1 fb-1

**H******** Mass Plots**

- Signal x 10

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## New elements of PTDR 2006 analysis:
Cut based analysis
Split into categories depending on photon reco quality and position
Usage of LLR for discovery, systematic
Optimized analysis* 
NN with kinematics and g isolation
s/b per event

|     CMS ECAL TDR |    CMS PTDR |  |               ATLAS |  |  |
| --- | --- | --- | --- | --- | --- |
|     NLO
count. exp |     NLO
cut based |      NLO
optimized* | TDR (LO) | New, NLO
Cut based | New, NLO
likelihood |
| ~ 7.5 |    6.0 |    8.2 |    3.9 |     6.3 |    8.7 |

**Significance for SM Higgs ****M****H****=130 GeV for 30 fb****-1**

- New elements of PTDR 2006 analysis:
- Cut based analysis
- Split into categories depending on photon reco quality and position
- Usage of LLR for discovery, systematic
- Optimized analysis*
- NN with kinematics and g isolation
- s/b per event

**Discovery Potential : ****H******

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## New elements of analysis
PT Higgs and WW bkg. as at NLO (re-weighted in PYTHIA)
include box gg->WW bkg.
NLO Wt cross section after jet veto 
Backgrounds from the data (and theory)
tt from  the data; uncertainty 16% at 5 fb-1
WW from the data; uncertainty 17% at 5 fb-1
Wt and gg->WW bkg from theor.  uncertainty 22% and 30%

**P****T**** Higgs and WW bkg. as at NLO (re-weighted in PYTHIA)**
**include box gg->WW bkg.**
**NLO Wt cross section after jet veto **
**Backgrounds from the data (and theory)**
**tt from  the data; uncertainty 16% at 5 fb****-1**
**WW from the data; uncertainty 17% at 5 fb****-1**
**Wt and gg->WW bkg from theor.  uncertainty 22% and 30%**
** **

**after cuts:**
**     ****- E****T****miss**** > 50 GeV**
**     ****- jet veto in******** < 2.4**
**     ****- 30 <p****T *****l***** max****<55 GeV**
**     ****- p****T**** *****l***** min**** > 25 GeV**
**     ****- 12 < m*****ll***** < 40 GeV **

**Discovery of ****H********WW********2*****l*****2******

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## Discovery Reach HWW2l2

- Branching Ratio at 95% C.L.

**CMS Physics TDR 2006****5******** Reach**** **

**very similar to old results w/o syst.**

**Discovery Reach ****H********WW********2*****l*****2******

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## Luminosity needed for 5  discovery

**Luminosity needed for 5 ******** discovery**

- 1 year at 10% of design luminosity

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## Higgs Mass Accuracy

***Stat. error only***

**Higgs Mass Accuracy**

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## CP Determination with HZZ4l

***d ************ (************) ~ H + ************I + ************ ******2****** A,***
***H scalar, A – pseudoscalar,***
*********=tan(************),  ************ = +/- ************/2 --> A***

**  ****C****2**** = ******** Br / ******** ****SM**** Br ****SM**** **

_**C**__**2**__** needed to exclude SM h**_

- CMS

- CMS

**CP Determination with H********ZZ********4*****l***

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## Hin association with top or W

**Discovery of Wh, h******

**Discovery of tth, h******

**Significance of tth, h********for 100 fb****-1**

**L=10****34**** cm****-2**** s****-1**

**L=10****34**** cm****-2**** s****-1**

**CMS**

**CMS**

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## qqH - Low mass H challenges

- D. Zeppenfeld et al.

- Higgs production in weak boson fusion
- Accompanied by jets in the forward direction
- Forward jet characteristics
- Lower jet ET (underlying event + pileup problem)
- Challenge for trigger and later analysis
- Trigger on higgs decay products
- Decays to HW(e/) W(jj) OK
- Low threshold electron/photon algorithm
- Decays to H(e/X) (h,X) OK
- Narrow jet tag - dedicated  algorithm
- Decays to two hadronic  and b-jets not OK
- Tag jets with location information (Perhaps at L1/HLT)
- Additional reduction in background
- Require two forward tag jets
- Require  between the jets
- CMS PTDR studies concentrated on decays to  using full simulation with pileup
- Decays to b jets (dominant but dirty)
- Still under investigation

**,W**
**,W**

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## qqH  W(l) W(jj) tag-jets

- Backgrounds considered:	t-tBar	Wbt	W+jets	Z+jets	WW, ZZ, WZ	QCD

- mH=160 GeV

- mH=170 GeV

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## Full simulation of qqH, Hl+j

**Discovery in Standard Model**

**discovery**
**of light h**
** ****in MSSM **

**CMS**
**SM**

**Full simulation of qqH, H*********l*****+j**

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## Signal Significance for 30 fb–1 

**with K factors**

**ATLAS h******** sensitivity is now comparable with CMS**
**CMS ttH, H********bb does not have even 3 ******** with 60 fb****-1**** **

**Signal Significance for 30 fb****–1**** **

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## Measurement of the SM Higgs boson coupling ratios

**ATL-PHYS-PUB-2003/030**

**Measurement of the SM Higgs boson coupling ratios**

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## Summary

- Higgs Discovery
- New CMS and ATLAS simulation results agree
- Inclusive h2 could be discovered with < 10fb-1
- Almost no change in the discovery potential withHZZ4*l* and HWW2*l*2
- tth, hbb is not discoverable by CMS even with 60 fb-1
- qqh, h  “survived” after full simulation
- The biggest discovery reach in MA-tan 
- Higgs Properties
- Mass measurement 0.1-1.0 % precision
- Width measurement 10-5 % precision, MH > 200 GeV
- CP with HZZ
- Ratio of couplings: ~ 5-30 %

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## Diffractive Higgs Trigger

- Rewarding if there is sufficient production
- Tagged protons give good MH measurement
- Since expected  is small, need all H decays
- Central detector
- Two Low PT jets from low mass Higgs decay
- Must tag as b-jets at HLT
- ||<2.5
- Essentially nothing else in the detector
- Require small HT - ETjet1 - ETjet2
- Pileup persists
- L1 rate for ~40 GeV jet thresholds is at 50 kHz, for L=2x1033 cm-2 s-1 running compared to bandwidth allocation of 1 kHz
- Proton taggers at L1
- Too far to be an integral part of trigger
- Detectors are 220m and 420 m away
- Trying to solve the problem by making quick correlations at the tail end of trigger processing

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## L1 output rate reduction with forward detectors

-  Very good reduction of rate in absence of pile-up both with T1/T2 veto
-  and with near-beam detectors at 220/420m
-  However, reduction decreases substantially in the presence of pile-up because
-  of diffractive component in pile-up

- Achievable total reduction: 10 x 2 (HT cond) x 2 (topological cond) = 40

- Can win additional factor ~2 in reduction when
- requiring that the 2 jets are in the same 
- hemisphere as the RP detectors that see the proton

- Jet
- isolation
- criterion

- For dijet trigger adding L1 conditions on the near-beam detectors provides a rate
- reduction sufficient to lower the dijet threshold to 40GeV per jet while still meeting
- the CMS L1 bandwidth limits for luminosities up to 2x 1033 cm-1 s-1

**L1 output rate reduction with forward detectors**

- Sridhara Dasu (Wisconsin) @ HLT Workshop II

## Pile-up background

-                          **~2 % with p @ 420m , ~6 % with p @ 220m**
- Translates into a probability of obtaining a fake DPE signature caused by protons from PU:

- At 1x 1034 cm-2s-1 60% of signal events have a protons  from PU faking DPE signatureThis is independent of the type of signal.

- Can be reduced by:
**Requiring correlation** between measurement of ξ and M in the central detector and
- in the near-beam detectors
**Fast timing detectors** that can determine whether the protons seen in the
- near-beam detector came from the same vertex as the hard scatter

**Pile-up background**

- Sridhara Dasu (Wisconsin) @ HLT Workshop II