Searches at the Run II Tevatron Collider

1 Leslie Groer, Columbia University Searches at the Run II Tevatron Collider CIPANP NY, May 22, 2003

Searches at the Run II Searches at the Run II Tevatron ColliderTevatron Collider

Leslie Groeron behalf of the DØ and CDF

Collaborations

Columbia University, New York

Conference on the Intersections of Particle and Nuclear Physics

New York City, NY May 22, 2003


Searching for New Phenomena at the Searching for New Phenomena at the TevatronTevatron

• Many different forms– Observation of the last unseen particle predicted by

SM • Higgs

– Discovery of particles not in the SM• SUSY, Leptoquarks

– Identification of new gauge interactions• W’/Z’, Technicolor

– Unexpected complexities beyond the SM • Compositeness

– Fundamental changes to modern physics • Extra dimensions

• Common theme - look for experimental signatures that could exhibit deviations from expectations– Prefer to set model independent limits

Outline• Tevatron Run II• CDF+DØ Detectors • Preliminary Results

– Higgs– New Physics

• Run II future prospects

• Conclusions


Tevatron Run II pp ColliderTevatron Run II pp Collider

’92-96 Run I 125 pb-1

top quark discovery ’96-’00 Accelerator and

Detector upgrades Main Injector and Recycler

rings Increased luminosity and

energy 2001-2005 Run IIa 2 fb-1

Upgrade Silicon and Trigger 2006 Run IIb 9-15 fb-1

--

Main Injector+ recycler

Tevatron

DØCDF

Chicago

Booster

p source

circumference: 6.2 km

• 1.8 TeV 1.96 TeV

– e.g. tt increase ~ 30%

• 6 p x 6 pbar 36 p x 36 pbar• Bunch spacing 3.5s 0.396s

Run II Delivered LuminosityTotal ~ 240 pb-1

Best week: ~7 pb-1

L = 4.5 x 1031 cm-2s-1


CDF & DØ Run II DetectorsCDF & DØ Run II Detectors

• Major upgrades to both detectors– New inner tracking chambers and silicon detectors– Extensions and improvements to muon systems and triggering– Complete replacement of trigger and DAQ elements for higher

rate• DØ: SMT, CFT, 2T superconducting

solenoid, preshowers, forward muon

DØ

CDF

• CDF: SVX, ISL, COT, TOF, plug calorimeters, intermediate muon


Hunting for the Higgs at the TevatronHunting for the Higgs at the Tevatron

• Production cross section and decays are all calculable within the SM

• Inclusive Higgs cross section ~ 1pb– gg fusion ~0.7 pb (MH = 120 GeV)

(very large background)– Associated production with W/Z

WH ~ 0.16 pb ZH ~ 0.1 pb– leptonic decays of W/Z help give

the needed background rejection• At higher masses, can use inclusive

production plus WW decays

• Decay channels

– For MH < 135 GeV, H bb

– For MH > 135 GeV, HWW

H bb H WW

g

g

Hb

b

t

Associated production

q

q

W

Hb

b

*W

0Z

q

qH

b

b

*Z

Gluon fusion

b-tagging and Mbb resolution & scale

are critical for a light Higgs !

H bb H WW

LEP 95% CLMH>114.4 GeV/c2


W/Z + Jets in Leptonic ChannelsW/Z + Jets in Leptonic Channels

• First step towards W(→lv )/Z(ll) + H(bb) measurement

• Major background: W/Z + di-jets• W+jets

– Isolated high pT lepton (e or ) with large missing ET

– Jets pT > 20 GeV in || < 2.5

Zll channelDi-jet

Invariant Mass Mjj

L = 35 pb-1

Wl channelDi-jet

Invariant Mass Mjj

L = 35 pb-1Dominated byJet energy scale systematic uncertainty

36 events ~340 events

• Z+jets– 2 high pT lepton (ee or

) with mass consistent with Z

– Jets pT > 20 GeV in || < 2.5

Improvements• b-tags• Jet and mET

resolutions• Optimize

analyses


HiggsHiggsW*W/W*W/ final states final states• HW*Wl+l- (search for dilepton + mET)• h (search for high pT isolated diphotons)• A lot of interest in these channels as could be

greatly enhanced by new couplings:– 4th generation– Fermiophobic or Topcolor Higgs

• Physics backgrounds: Z/*, WW, tt, W/Z+jets, QCD• Use spin correlations to suppress background

contributions in leptonic mode()• Derive .Br limits assuming BR = 1 HW*Wl+l-

h


CDF Searches for H++CDF Searches for H++

• LR Symmetry breaking: SU(2)L x SU(2)L x U(1)B-L SU(2)L x U(1)L

• Higgs fields are a left-right doublet (½,½,0) and 2 triplets:• SUSY models suggest low mass doubly-charged Higgs

H++ Properties and Selection:• Pair (*/Z exchange) or singly (WW fusion) produced in pp

collisions• Same sign leptons decay mode provide strong experimental

signature• Inclusive electron trigger used (915.3 pb-1)• Two central same-sign

electrons required• MH 10% dielectron

mass windows explored

• Acceptance 20-35%• 0 events observed• Bckd: 0.60.5


Limits on new Neutral Gauge Limits on new Neutral Gauge Bosons Z’Bosons Z’

DØ Run II Preliminary

L = 50.0 pb-1

DØ ee channel

Run I: MZ’ > 670 GeV

CDF e + combined

Run II(ee): MZ’ > 650 GeV/c2

Run II(): MZ’ > 455 GeV/c2

Run I (ee): MZ’ > 690 GeV /c2

L = 72 pb-1

• Neutral Gauge Bosons Z’– Assume SM couplings

• Searches in both ee and channels

• No excess observed in e or channels

• Bckds: DY, QCD misid electrons, WW, WZ, tt


Mgraviton Lum Hewett

TeV pb- 1 GRW n=2 n=7

di- EM 50 1.12 1.16 0.89 1

dimuon 30 0.79 0.68 0.63 0.71

Run I (EM) 110 1.2 1.37 0.97 1.1

HLZ

Searches for Large Extra DimensionSearches for Large Extra Dimension


• Assume SM particles are confined to a 3D-brane

• Gravity propagates in the extra dimensions

• Signature is an excess of high mass dilepton and diphoton events from virtual KK graviton diagrams

• Angular distribution asymmetries arise from inteference terms

• DØ searches in diEM and dimuon– Invariant mass– Cos * (* = scattering

angle in rest frame)

di-EM


e+e+ combined combined

R-S Extra Dimension SearchesR-S Extra Dimension Searches

• Excited graviton in 5 dimensions

• Kaluza-Klein Modes lead to observable spin-2 resonancesG

• Free parameters: mass MG and coupling k/MPL

Dielecton: MG’ > 535 GeV/c2

Dimuon: MG’ > 370 GeV/c2

• Look for high mass excess in Drell-Yan dilepton events

• CDF searches in ee and channels


• Gravity Mediated SUSY• LSP is a light (<< 1 keV) gravitino,

phenomenology driven by nature of the NLSP (0)

• Signatures include 2 and missing ET

• DØ search

– Require two photons with pT > 20 GeV, apply quality and topological cuts

– 0 events observed– QCD fake background

determined from data (1.6 0.4)• Derive limits in Snowmass model • 95% CL on : 51 TeV gives

equivalent limit on Snowmass model gives M(0) > 66 GeV

• Run I limit: > 75 GeV

New Physics Searches in Diphoton New Physics Searches in Diphoton ChannelsChannels

ET


EETT//

L = 50.0 pb-1

Theory = "Snowmass“ slope:M = 2N

5 = 1

tan = 15, > 0

M0 > 66 GeV/c2


GG~~~0

1


Limits on New Physics in the eLimits on New Physics in the e+X +X channelchannel

Cross-section Limit as a function of missing ET

• Very low backgrounds → pursue analysis in a model-independent way

• Require e,pT > 15 GeV, estimate fake rates from data, physics backgrounds from simulation

• 13 events, 9.6 2.7 exp. background(Z, QCD+W+jets, WWe, tt)L = 33.0 pb-1

A* new physics(e.g. acceptance for WW→e ~ 17%)

• At low MET physics backgrounds dominate, at high MET instrumental effects

• Complementary search in jets + MET• Sensitivity at the 0.1 pb level already


Search in Trileptons: eel + XSearch in Trileptons: eel + X

• Typical selection efficiency for SUGRA 2-4%

• Sensitivity still about factor 7 away from extending excluded area in parameter space

• working on improving efficiency, adding channels

• Start from dielectron sample: understand trigger, reconstruction, simulation• Also verify determination of QCD fake background (from data)• Main backgrounds: Zee, and We)

.Br(3 leptons) < 3.5 pb (95% C.L.)Backgrounds Data

313210 GeV < M(ee) < 70 GeV 721

123

3

0

pT(e1) > 15 GeV, pT(e2) > 10 GeV 3216 ± 43.2660.2 ± 19.1

MT > 15 GeV 96.4 ± 8.1Add. Isolated Track, pT > 5 GeV 3.2 ± 2.3Missing ET > 15 GeV 0.0 ± 2.0

L = 42.0 pb-1

~~~~ 01

021 leepp


New: CDF Search for Excited Electrons New: CDF Search for Excited Electrons e*e*

• pp e* + e e + e (U. Baur PRD42, 3, 1990)

• Compositeness scale • Reconstruct M(e) in ee events• Bckds: Z, Z+jet, Multijet, W+jets• No events observed in 72 pb-1

• New Limit on e* mass is 785 GeV (=Me*)

• Previous limit from H1 was 223 GeV


Searches in heavy flavor: tau Searches in heavy flavor: tau leptonsleptons

• Measurements of tau leptons important for tests of the SM and in the Higgs and SUSY sectors – Large backgrounds from jets– Multivariate techniques useful

• Both experiments have established a Z eh signal

• CDF has measured .B(W h)

Ntracks

L = 50 pb-1

OS-SScollinear approximation

14 9 data, 13 4 expected

• DØ also seen Z h using NN techniques

CDF Z

.BR(W) = 2.62 0.07stat 0.21sys 0.16lum nb .BR(Wl) = 2.69 0.1 nb (NNLO)

L = 70 pb-1

CDF Run II Preliminary

DØ Zeh


Search for LeptoQuarksSearch for LeptoQuarks

• Extended gauge sectors and composite modelsLQ

• Directly couple leptons and quarks

• LQ lq or q, =BR(LQlq)

• Search for dilepton + jets and reconstruct LQ mass- or -

• Search for mET and dijets

• Limits depend on coupling

• Assume =1 or 0 for limits

LQ

LQLQ

LQ

L = 40.0 pb-1

MLQ2 > 157 GeV/c2

Run I >200 GeV

MLQ1 > 230 GeV/c2

Run I > 220 GeV/c2

60 < MLQ > 107 GeV/c2

DØ LQ2

CDF LQq

42 events, bckd: 4311

0 events, bckd: 3.43


- Inclusive jet sample

- 2 highest ET jets, ||<2

-

Search for Resonances in DijetsSearch for Resonances in Dijets

• Test QCD and sensitive to high mass resonances• Both experiments have measured dijet cross-section in Run II

– Agreement so far with SM expectations

• No significant excess beyond the Standard Model

- Fit mass spectrum with simple background parameterization

- Search for bumps comparable with the mass resolution

• Derive mass limits on the BR for various exotic particles


To set limits useTo set limits usestable stopstable stop

modelmodel

CHACHArged rged MMassive stable assive stable PParticlesarticles

TOF• Long lived particles escape without

decaying• Look like isolated slow-moving high-pT

muon• Use TOF and look for t(TOF) –t

(interaction)• Derive limit on production• Interpret 95% CL limits in stable stop

model– M(isolated stop) > 107 GeV/c2

– M(non-isolated stop) > 96 GeV/c2

• Limits independent of details of SUSY• Previous limits from ALEPH: M > 95 GeV


ConclusionsConclusions

Run II is well underway• We have commissioned all the detectors and have initial physics

results

– Cross-sections: W/Z, b-quarks, jets, B-lifetimes, rediscovered top

– New phenomena and Higgs searches are underway!

– Many results already competitive with Run I

• Excellent performance of new tracking systems

• CDF L2 Silicon displaced Vertex Trigger a great success

• DØ Silicon Track Trigger online by this summer

• Fully exploiting the luminosity delivered by the Tevatron

– New Physics results this summer (LP03, etc) + publications

– Sensitive at the 0.1 pb and 1 TeV scale in many channels

• Joint working group re-evaluating the Tevatron Higgs reach

• CoM Energy (~ x1.3-2), luminosity (~ x20-50), better detectors and analysis techniques (~ x2?) ~ x100 increase in sensitivity for some channels

The Tevatron will be the place for high-pT for the next few years


BackupsBackups


CDFII DetectorCDFII Detector

Retained from Run ISolenoid (1.4 Tesla)Central calorimetersCentral muon detectors

New in Run IITracking system

Silicon vertex detector (SVXII)Intermediate silicon layersCentral outer tracker (COT)

End plug calorimeterIntermediate muon detectorsTime of flight systemFront-end electronicsTrigger systemDAQ system

COT

0

.5

1.0

1.5

2.0

0 .5 1.0 1.5 2.0 2.5 3.0

END WALL

HADRON

CAL.

30

300

SOLENOID

= 1.0

= 2.0n

EN

D P

LUG

EM

CA

LOR

IMETER

EN

D P

LUG

HA

DR

ON

CA

LOR

IMETER

= 3.0n

n

m

m

Inner Silicon Intermediate Silicon

Time of Flight


DØ Inner Tracking VolumeDØ Inner Tracking Volume

(2T)


• The Higgs discovery potential for Run II was evaluated(hep-ph/0010338) using a parameterized fast detector simulation

• Discovery at 3-5 can be made

– Combine all channels, data from both D0 and CDF

– Improve understanding of signal and background processes

• b-tagging, resolution of Mbb

• Advanced analysis techniques are vital• Largest luminosity required to discover Higgs• Reevaluation of the expectations with real detector simulations and

Run II experience underway at the moment

Tevatron Higgs Working Group Tevatron Higgs Working Group

LE

P e

xcl

ud

eda

t 95

% C

.L.

Fermilab Run II Higgs Workshop


114 GeV 200 GeV

Searching for the HiggsSearching for the Higgs

• Focus has been on experiments at the LEP e+e–

collider at CERN (European Laboratory for Particle Physics) – Fits of electroweak data from precision

measurements of parameters of the W and Z bosons, combined with Fermilab’s top quark mass measurements, set an upper limit of mH ~ 200 GeV

– direct searches for Higgs production exclude mH < 114.4 GeV/c2

– Much of the favored region already excluded

• Fermilab Tevatron Run II has an exciting window of opportunity before LHC turn on


Tevatron Luminosity Goals: 2003Tevatron Luminosity Goals: 2003

• Base– 200 pb-1 for FY03– 10 pb-1/week by year end

• Stretch– 320 pb-1 for FY03– 15 pb-1/week by year

end• FY02

– 80 pb-1 for the year– 6.7 pb-1 best week

best

luminosity 1 year ago

highest luminosity

to date

FY03 stretch goals

max. antiproton stackrate (E10/ hr) 10.2 13.1 18

max. antiproton stacksize (E10/ hr) 100 149 200

pbar xfer eff. .44 .66 .80

pbars/ bunch at low beta (E9) 8.7 25.1 31.0

protons/ bunch at low beta (E9) 126 205 240

peak luminosity (E31 cm-2sec-1) 1.18 4.06 6.6


Tevatron Luminosity ScenariosTevatron Luminosity Scenarios

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Fiscal Year End

Ru

n I

I In

teg

rate

d L

um

ino

sity

(p

b-1

)

10/02 Projection Stretch 10/02 Projection Base

End of Run IIbDetector upgrades complete

Limit of Run I Silicon

Earliest date forLHC physics


ExpectedExpectedbb mass resolutionsbb mass resolutions

• Directly influences signal significance• Requires b-jet specific energy corrections (semi-leptonic,

fragmentation)• Z bb will be a calibration signal for b-jet energy corrections• To improve mass resolution, combine tracks with calorimeter

cells for jet energy measurementCDF observation in Run I Z bb

Higgs simulation for 2 x 15fb-1 (2 expt’s)

Higgs

Jet energy corrections

Z

mH = 120 GeV


SUSY Higgs Production at the TevatronSUSY Higgs Production at the Tevatron

• bb(h/H/A) couplings are enhanced at large tan (= ratio of v.e.v’s) ~ 1 pb for tan = 30 and mh = 130 GeV

bb(h/A) 4b

oneexpt

CDF Run 1 analysis (4 jets, 3 b-tags)

sensitive to tan > 60

Preliminary

increasingluminosity


+ jet sample

b-tagging b-tagging

• b-tagging explores IP significance method• Lepton from semileptonic decay of b is very useful

Positive IP

Negative IP

• Impact Parameter > 0 track crosses jet axis after primary vertex

Jet

Jet

track

track

Resolution

b enhancedInteraction point

Interaction point

• Impact Parameter < 0 track crosses jet axis before primary vertex

Significance = IP/IP


B-taggingB-tagging

• B-tagging is crucial for light Higgs search to reject light-quark content

• Estimated efficiency and fake rates from impact parameter resolution– b-tag efficiency ~60%– c-quark mistag rate ~15-20%– Light quarks (u,d,s) mistag rate ~few %

• Ongoing improvement in alignment and track-finding efficiency

High-pTrel muon sample

MC


SUSY search Run I (120 pb-1) Run II

Jets +mET (new) --------- x < 4.2 pb (4.1 pb-1)

mET >70 GeV

e +mETA x <0.1 pb (33 pb-1)

mET >45 GeV

lll+mET (Run I)

eel+mET (Run II)

x BR< 0.3 pb

M(0)60 GeVmET >10-15 GeV

x BR< 2.2 pb (42 pb-1)

M(0)=62 GeVmET >15 GeV

Analysis Run I (120 pb-1) Run II

SUSY 2 + mET M(0) > 75 GeV M(0) > 66 (40 pb-1)

1st LQ 2 e + 2 jets MLQ > 225 GeV MLQ > 179 (43 pb-1)

2nd LQ 2 + 2 jets MLQ > 200 GeV MLQ > 157 (30 pb-1)

LED 2em MS> 1.1 TeV MS> 1.0 (50 pb-1)

LED 2 (new) -------MS> 0.71 (30 pb-1)

DØ Search ScorecardDØ Search Scorecard


Run IIa ProspectsRun IIa Prospects

• Towards the next few years:

Sample

W’lZ’ll

WV (W’l, V=W,,Z)

ZV (Z’ll, V=W,,Z)

tt (mass sample, 1 b-tag)

Run I

77k10k903020

Run IIa

2300k202k1800500800

Event yields per experiment (2 fb-1)

MW~40 MeVMt ~ 3 GeV

DØ / CDF

Run 2aPredicti

on


Run IIB UpgradesRun IIB Upgrades

• Both detectors were designed to withstand ~2-4 fb-1 with an average of ~2-3 interactions per crossing– Integrated luminosity limited by radiation

damage to silicon tracker– Instantaneous luminosity limited by trigger

rejection• Tevatron goals for Run IIb are to accumulate

5-15 fb-1 with an average of ~5 interactions per crossing, necessitating – Replacement of silicon trackers

• Similar design for both and common SVX4 chip

– Replacement and upgrades to few key trigger and DAQ components for high-pT physics program

• Run 2 to continue in 2006 following ~7 month shutdown

• All critical elements have been prototyped, sensor procurement has begun

CDF

DØ

CDF

The “Luminosity The “Luminosity Lift”Lift”

New physics panoramas open up each time we take the “Luminosity Lift”

Searches at the Run II Tevatron Collider

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