# Presentation: 678100

## Run II perspective at CDF:top, higgs & searches

- Patrizia Azzi
-  INFN Padova

## The Tevatron upgrade

- Two possible crossing times:
-  396 ns for 36  bunches
-  132 ns for 108 bunches
- Average number of overlapping interactions in a given beam  crossing:
**N = 3** for Linst = 1x1032 cm-2 s -1    @396 nsec
**N = 2** for Linst = 1x1032 cm-2 s -1   @132 nsec

-  ******s = 2.0 TeV   **
** ****L****inst**** ****up to 2x10****32**** cm****-2**** s****-1**
- Two data taking periods:
-   Run IIA Lint=1÷2 fb-1
-   Run IIB Lint=10÷15 fb-1

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## CDF II Detector Upgrade

**End Plug Calorimeters **
**extended to larger ******

**CDF II Detector Upgrade**

**CTC replaced **
**by COT**

**New Silicon **
**Tracking System**

**Time-of-Flight**
**(TOF) added**

*Upgrade will *
*allow operation*
*at high luminosity*
*and extend physics*
*capabilities*

**New Electronics, **
**Trigger, DAQ**

**Muon System upgraded**

**Forward Calorimeter**
**eliminated**

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## The CDFII Tracking System

_**Central Outer Tracker**_ : open cell drift chamber
- maximum drift time 100ns
- Small cell size, Fast gas
- single hit resolution ~200 m
- excellent pattern recognition
- improved stereo capabilities
_**Silicon Tracker System:**_
- increased *z* coverage (length ~ 1m)
-  coverage up to |  | < 2
- 3-D track reconstruction
- impact parameter resolution
-  < 30 m
- z < 60 m
**3 different subdetectors: **750,000 channels
**L00**:  inner most, r =  2.5cm, rad-hard, single sided
**SVXII: ** 5 layers,  3 < r < 10cm, double sided  (90 and sas)
**ISL:** 2 layers, 10 < r < 20 cm and large double sided

_**Trigger System**_: two main  improvements
**XFT**: track reconstruction at L1
**SVT**: displaced track triggering at L2

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## Top pair production & decay

- Strong production at s = 2 TeV has pp  tt+Xpb for mt=175 GeV/c2
- 40% increase wrt s=1.8 TeV
- qq is 85% and gg increases by 15% wrt s 1.8 TeV
- Dominant decay mode is weak through t Wb
- Vtb as in CKM matrix
- Final states subdivision based on W(‘s) decay (l=e,:
- Single lepton:  	  BR= 30%
- Dilepton:          	  BR=  5%
- All hadronic:    	  BR= 44%
- +lepton and/or jets: BR= 21%

- A

- B

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## Production of single top through Wg fusion and W* is about 1/3 of strong pair production (for mt=175 GeV/c2 @ s=2 TeV): 
W-gluon fusion: (Wgtb+X)= 1.44 pb 
Virtual W(W*tb+X) = 0.74 pb 
large uncertainties in the cross sections!

Effective isolation of W* process will be tried at Tevatron: 
At LHC suffers from larger background of gluon initiated processes
Top decays before hadronizing, polarization info is preserved in decay products
Useful to disentagle combinatorics in mass reconstruction.

*W-gluon fusion*: ******(Wg********tb+X)= 1.44 pb**** **
*Virtual W*******(W*********tb+X) = 0.74 pb**** **
- large uncertainties in the cross sections!
- Effective isolation of W* process** **will be tried at Tevatron:
- At LHC suffers from larger background of gluon initiated processes
- Top decays before hadronizing, polarization info is preserved in decay products
- Useful to disentagle combinatorics in mass reconstruction.

**Single Top production**

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## Run II detector improvements (in one page)

- Improved z coverage of Silicon tracker  *+50% of Run I geometrical acceptance*
- 3D vertexing capabilities  *better fake rejection*
- Track reconstruction can be extended to 1<<2  *several major effects:*
-  *btagging (recover ~30% of b’s in ttbar events) *
*lepton ID (electrons in Plug calorimeter)*
- Increased muon system acceptance by 12%  *affects trigger, ID and SLT efficiency*

*Net result:*
*Cleaner tt samples w/ smaller background. *
*Single top samples (less clean)*
*Larger control samples to reduce systematic uncertainties *

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## Top physics measurements“the basics”

_**Top quark mass:**_ fundamental SM parameter
- needed to determine ttH coupling
- important in radiative corrections:
- for M(W)=20 MeV/c2 and m(t)=2 GeV/c2, m(H) is constrained to within 50% (best constrain from a single experiment!)
- Experimental handles:
- Double b tagging: reduce overall background & combinatorial
- Data driven systematic scale with 1/N (jet energy scale, gluon radiation)
_**Production cross section: **_  fundamental test of QCD
- discrepancies from QCD might imply non SM physics
- Current uncertainty is statistic dominated
- Experimental handles:
- Larger overall efficiency (lepton ID, trigger, btagging) w/ better background rejection
- Main systematics (jet energy scale, ISR, btag)scale with 1/N

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## Top physics measurements“the new stuff”

- Branching Ratios:
- B (t(b)W): from **ratio of double to single tagged events**
_*Indirect *_Vtb(Run I)= 0.99±0.15 (>0.76 @95% C.L.)  **down to 3% (1fb****-1****)**
- B (tb(W)):  from **ratio of dilepton to single lepton events**
- Process candidate is t->H+b: the sensitivity is related to the mass and width of the H+ and to the fact that BR(H->cs)=100%. If m(H+)>m(W) and BR(H->)0  limits get worse
**10fb****-1**** of data will exclude m(H+)<m(W) for “any” value of tan********gap!)**
- W helicity: since the top decays before hadronizing the helicity info is preserved.
- SM predictions is: B(tbW0)=69.2% for m(t)=170 GeV/c2
- Run I measured: F0=70.6±1.6%
-  **V-A and V+A probed with a % level precision in Run II (10fb****-1****)**** **
- Rare decays:
- FCNC in Run I: BR(t->Zc)<33% @95% CL, BR(t->c)<3% @95%CL             **down to 10****-2****÷10****-3**** @95%CL**
- In Run II may become visible the CKM suppressed decays:
- BR(t->Ws)~0.1% , BR(t->Wd)~0.01%. No analysis strategy yet!

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## Single top measurements

- Single top physics: all new! Single top samples less clean
- Analysis strategy:
- Single high pt lepton and missing energy from W + btagged jets
- look for Wb invariant mass peak
- use btagged jet to help solve ambiguities
- Main measurements: production cross section(s), mass, Vtb
- Challenging: separation of the 2 production modes:
-  W* not viable at LHC, swamped by gluon initiated processes
**In Run II possible:  ******** =10% and ********V****tb**** =20% in W* channel **
- Not competitive with the use of the full sample, but different systematics involved.
- CP violation from asymmetries in single top production:
- with 200 events A=0.15

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## Higgs production & decayat Tevatron

- Dominant processes @s=2TeV:
- Gluon fusion
- Higgs*strahlung*
- Vector boson fusion

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## Higgs searches in Run I

**Higgs searches in Run I**

_**MSSM Higgs**_**, pp********b********b where ********=h,H,A**
- at large tan mh mA  (mA < 125 GeV)
- mH mA (mA > 125 GeV)
- multijet sample +  3 b-tags
- Limits:
- Min stop mixing: mh (max) = 115 GeV
- Max stop mixing: mh (max) = 130 GeV

_**SM Higgs**_**, pp********VH associated production:**
-  l+ jets (1 btag)
-  MET + jets ( 2 b-tag)
- multijets (2 btag)

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## Tools for Higgs in Run II

- Main tools:
- improved b-tagging  (3D silicon + large    75%  efficiency for jet ET >35 GeV )
- improved bb mass resolution (from Zbb studies)
- improved lepton acceptance & ID
**new specific triggers** to recover acceptance in most of the channels (displaced track trigger, multijet, etc.)

- Production cross section is limited!
- Signature less striking than tt:
-  *smaller number of jets*
* **smaller invariant mass*

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## Run II SM Higgs sensitivity

- Performances by channels in 1fb-1 assuming M(bb)=10%

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## ttH (PRL 71 2699 (1993))

**Light Higgs: m(H)<140 GeV/c****2**
**M****H ****= 120 GeV/c****2****, 15fb****-1 ****of data **
- ~7 signal events: very distinctive!
- ~12 ttbb background
- ~2 ttcc background
- Reconstruct top: reconstruction efficiency depends on combinatorial, btag efficiency and purity (Ntag3)
***optimistic 70% reconstruction efficiency***
- 2.8 sigma significance in RunIIB

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## Strategies for searches in RunII

- Two coexisting approaches *need to be both pursued in a balanced way:*
- A) Traditional model driven analyses
- pick a favorite theoretical model           ****** might become soon outdated!**
-  pick a process, choose the best signature(s): optimize selection acceptances based on signal MC
- calculate the background                                  ****** best optimization!**
- evaluate the limit or discovery your signal
- B) Signature based approach
- pick a specific signature ( i.e. diphoton+X)
- define your sample in terms of known processes         ****** hard work!**
- publish estimates of acceptances & cross section information useful for theorists
- see an excess? Inconsistency with SM?  Test one or more models later
-          ****** ****not best optimization but...******** open to a whole lot of models! ****Study unbiased and fundamental for data understanding**

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## Supersymmetry Intro

- SM Fermions              Boson Superpartners
- SM Bosons                 Fermion Superpartners
- Physical SUSY sparticles: *neutralinos (Higgs, Photon, Z partners), charginos  (Higgs, W partners), squarks  (quark partners), sleptons  (lepton partners) *
- Supergravity
- SUSY broken near GUT scale
- GUT scale parameters + RGE’s          SUSY spectrum
- Some parameters: scalar mass       , gaugino mass         , ratio of Higgs v.e.v’s  *tan***, Higgs mixing parameter
- Gauge-mediated models: SUSY broken at lower energies – breaking scale F an important parameter.
- Gravitino      plays important role in phenomenology
- Lightest SUSY Particle (LSP) often       (SUGRA) or        (GMSB)
- R-Parity: -1 for SUSY particles, +1 for SM particles
- If conserved: LSP stable, carries away missing ET

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## In between SBS and model based searches: 
MET:
Crucial for all searches with  stable LSP
Trileptons:
Signature of                      
R-Parity Violation 
Dileptons:
squark/gluino, chargino/neutralino & R-Parity Violation 
Flavor Tagging + leptons + MET:
 scalar tops (stops) and scalar bottoms (sbottoms)
Photons:  
useful for GMSB

- MET:
- Crucial for all searches with  stable LSP
- Trileptons:
- Signature of
- R-Parity Violation
- Dileptons:
- squark/gluino, chargino/neutralino & R-Parity Violation
- Flavor Tagging + leptons + MET:
-  scalar tops (stops) and scalar bottoms (sbottoms)
- Photons:
- useful for GMSB

**SUSY Signatures **

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## Squark/gluino search

- MET+jets analysis:
- large BR, large background (QCD + fake MET,                           )
- Use MET trigger
- Use *Blind Box* search method
- Define signal region as:
- MET>70 GeV
- ETjet1+ETjet2+MET = HT>150 GeV
- No isolated tracks (lepton veto)
- Run I result:
- 76.02±12.8 events expected
- Observed 74
- Run II projection: probe squark/gluino masses up to ~400 GeV/c2
- lower MET trigger treshold (less noise in CDF from Main Ring)

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## Squarks searches in Run II

-                                                              _**Missing  E**__**T**__** sample:**_
-                                                             1) Reduce cosmic/instrumental background;
-                                                                              2) 3 jets, one central
- 3) Topology requirements between jets and MET vector;
- 4) Kinematic requirements on HT -like quantities (ET ( jet1) + ET ( jet2) + MET);
- 5) Lepton veto ( to get rid of W,Z,tt )

- 41%

- 31%

- 57%

- Run I analysis

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## Stops and Sbottoms

- Stops may be light due to mixing between partners of left, right-handed top
- Similar for sbottoms
- Look for direct pair production of stops or sbottoms

- Stop mass reach up to ~175GeV/c2
- Sbottom sensitivity up to 250GeV/c2

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## Commissioning Run2-Jet event

**Jet Et>200 GeV!!!**

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001

## Track/muon trigger

- Muon hit

- Track pointing
- To muon hit

- Lake Louise Winter Institute, Alberta (CA)  February 18-25 2001