searches for new physics with cdf else lytken, purdue university

Searches for New Physics with CDF

Else Lytken, Purdue University

Else Lytken, March 30, 2006 2

Outline o Introduction to the Tevatron and CDF o CDF search strategieso Selection of results:

o Higgs searcheso SUSY searcheso Other searches:

bump hunting, model-independent

o Conclusions


The Tevatron

p-p collider located at Fermilab ~ 50 miles from ChicagoRun II started in Spring 2001

anti-protons: electron coolingaccumulation: up to 20 mA/hourRoutine operation of storage rings

Beams collide every 396 ns with s = 1.96 TeVCurrent luminosity record:

1.8*1032 cm-2s-1

26.1 pb-1 in a week

Plan: Take data until 2009, collecting a total of 4-8 fb-1

by end of Run II

_

2km

1mA ~ 1010 p_

^


Collider Detector @ Fermilab

Had Calorimeter

Muon system

Drift chamber

Em Calorimeter

=0=1 Inner tracker (Si)

Towers 150() x 0.1()

Central:

/E = 13.5%/ET

Extends to ||~3.8

/E = 0.5/E coverage:||< 1.2

Hit res: 140 microns

coverage: ||~2.0IP res: 40 microns

Basic coverage ||<1.0

Extension: ||<1.5

B field: 1.4 T


PerformanceRun II now mature environment stable operation of acceleratorand detectorsMore than 1fb-1 of data on tapeAnalyses shown here use up to 1fb-1 (< when corrected for running conditions)

10 Run I dataset!

1fb-1


Leptons and jetsAll searches highly dependent on efficient and reliable object identification

Typical efficiencies: (Jet fake rate ~ 10-3 - 10-4 )

~ 45% at high pT

Calorimeter towers:

Coverage : ||<3.6

Heavy flavour jets (||<1.5) : Identified by tagging soft leptons or secondary vertex.

e Eff: 80-90% ~ 80% 85-95% ~50%

Coverage ||<2 ||<2.8 ||<1.5 ||<1


New PhysicsThe standard model has been a great success Too many questions blowing in the wind:

hierarchy problem, divergences at high E, how to explain dark matter, etc.

Something else is out there to take over at higher energies.Tevatron is currently the place to search for new high pt physics!

Some of the focus points for CDF searches:SM and Extended higgs sectorSupersymmetry

Extra dimensions (large or universal) New heavy gauge bosons Compositeness Generic signature-based searches – always preparing for

the unexpected!Very extensive program, please check out http://www-cdf.fnal.gov/physics/exotic/exotic.html for more results


p pNEW PHYSICS

Large Missing Energy

Multi-Leptons

Heavy Flavor Jets

Multi-Photons

Long Lived Massive Particles

(ET, or MET)/

New resonances

What we look for


Expecting small excesses above SM+ many studies have to rely on predictions from simulation to test standard model prediction

very sensitive to little imperfections (detector material distribution, tracking resolution, etc.)

•Now 2-3 interactions/bunch crossing, and increasing with increasing Tevatron L

σ(W→lν)

σ(tt)mt=175 GeV

Challenges for New Physics

most analyses unbiased searches: Signal regions not looked at until confident in background estimates


Standard Model Higgs- Higgs is only missing SM particle

needed to gives masses to W, Z, fermions - Higgs-like object necessary for most beyond-SM theories.Direct bound from LEP2: mH >114.4 GeV

Indirect from precision EWK fits: mH <175 GeV (<207 GeV if low mass area excl )

Preferred higgs mass (89 GeV) already excluded

Includes new top mass from TeV:mtop = 172.5±2.3GeV


Higgs Searches @ TeVatronTevatron strategy:

Low higgs masses: (<135 GeV)

Associated higgs production

WH, ZH, with Hbb

(single higgs dominated by dijet background)

Cross section is few hundred fb-1 and efficiencies a few %

Very challenging

For mHiggs>135 GeV:

gg H with HWW*

cros

s se

ctio

n (p

b)

SM Higgs cross section (HIGLU,V2HV)

pp,s=1.96 TeV-


WHlbb

Search for resonant mass peak in dijets1 tag: 175±26 expected, 187 observed2 tags: 15 ±3 expected, 14 observed

Same final state also used to set limit fortechni- given mass of techni-

Among best channels for low mass higgs• 1 high pT lepton (e or µ)• MET > 20 GeV• 2 b jets ( at least 1 tagged)Main background: Wbb, Wcc, top


Light flavormistags

QCD

Top

EWK

ZHbb

MET=145 GeV, dijet mass: 82 GeV

In mass window 80-120 GeV:

SM prediction: 4.36 1.02 events

Observe: 6 events.

Background composition:

QCD normalized in control region:

Jet ET = 100 GeV, tagged

Jet ET = 55 GeVtagged

Select events with• 2 jets (at least 1b-tag)• Missing Et >70 GeV

Candidate event:


HWW*

Spin 0 higgs: spin of W’s from H back-to-back leptons have small angularseparation and small inv mass

W+ e+

W- e-

• Look for opp sign dileptons + MET>25 GeV• Veto Z mass windowMain bkg: direct WW production


HWW* resultsSuppress background: Mass cut, Mll<½MH and fit to

No excess observed, overall see 14 events as expected

ee e llTotal bkg

4.5±0.4 6.6±0.6 2.9±0.3 14.0±1.3

HWW 0.11±0.01 0.23±0.01 0.11±0.01 0.44±0.03

Obs 4 5 5 14

150 GeV Higgs


Higgs Searches: CDF Combined Results

In addition to more data: Several improvements underway to bridge the gap


SupersymmetryIdea: extend SM with symmetry fermions bosonsIf realized, lots of new particles to be found!

Many attractions: Low scale supersymmetry protects higgs mass, provides dark matter candidate, unification @1016 GeV, and consistent with precision top mass fits

Spin 0 1/2 1 3/2 25 higgses leptons gauge gravitino gravitonh0/h0,H0,A, H± quarks bosons G Gsleptons l gluino gsquarks q gauginos ±

0~

~~

~~

~


SUSY@TeVatron

Large selection of SUSY models and parametersMost interpretations use minimal models

with tan= vu/vd, m0= scalar mass, m1/2= fermion mass

Non-exluded cross sections small Compared to LHC expectations:

Tevatron

LHC


SUSY signatures

SUSY searches attractive from experimental point of view due to variety of signatures:

- Missing transverse energy from stable LSP’s

(when R-parity conserved)

- multijets from cascade decays

- multileptons

Lightest SusyParticle

New quantum numberoften assumed conserved

R PB L s ( ) ( )1 3 2 +1 SM

- 1 SUSY


MET + 3 leptonsExpected signature from chargino-neutralino productionHeavily constrained by LEP: m() >103 GeV

~02

~

1

W*

q

q ~01~

1

W*

~01

~02

Z*

Clean signature very attractive for Tevatron, Main backgrounds: DY+fake lepton/conversion, W(Z/*)

CDF takes advantage of all lepton triggers for maximum sensitivity

1

’


3 leptons: continued

All observations in agreement with SM predictions

ChannelExample signal

SM expected

Obs

µµ/e +l (0.7 fb-1) 2.3±0.3 1.2±0.2 1

ee+l (0.35 fb-1) 0.5±0.06 0.2±0.05 0

µµ+l (low pt) (0.3 fb-1) 0.2±0.03 0.1±0.03 0

ee+trk (0.6 fb-1) 0.7±0.03 0.5±0.1 1

Stay tuned for updated limits!

(enhanced sensitivity to ’s)


Like-sign dileptons (704 pb-1)

Signature for leptons, decays of gluinosor other majorana particles leptons

Most problematic background: untagged conversions, Drell-Yan+ and W+

MET>15 GeV to suppress DY

Opp sign leptons Like-sign from conversions


like-sign resultsCategory Obs Predicted signal

ee 4 2.6 ± 0.4 0.64

eμ 5 3.5 ± 0.6 1.64

µμ 0 0.7 ± 0.1 0.91

Total 9 6.8 ± 1.0 3.19

Interesting excess at high pT

- number of events consistent with background prediction.

Look forward to add more data!


RP: 4 leptons (350 pb-1)

Assume prompt decay of LSP 4 leptons from decaysAnalysis also looked at 3 leptons

~~

Yukawa term:

ijkLiLjEk

Analysis accepts e and µSensitive to 121 and 122

_

Trilepton control regions

Striking signature, virtually no SM backgroundNo cut on MET or N jets4 Leptons: Expects 1.5±0.2 signal, <0.01 SM, observes 0

Comb. 1210: < 0.21 pb limits 1220 : < 0.11 pb

/

:


MET + jets: squark and gluinoGeneric squarks and gluinos strongly producedCross section @ Tevatron: ~ a few pb

Expect cascade decaysSignature: lots of MET and 2 jets

• Req. 3 jets and MET>165 GeV

• Bkg dominated by Z + jets

• Check: compare data and QCD MC in jet domimated region

• SM wins again:

Expect 4.10.6 events, observe 3


Search for StopProduction of 3rd generation sparticles could give us first hintsof SUSY:

Due to larger masses of SM partners, mass eigenstates ofleft- and right- stops can have large mass splitting. lightest stop, t1, lighter than other squarks

CDF looking into severalpossible decay modes: t1 c t1 bl RP modes: t1 b New result also using HT:

mass(LQ3)368 GeV Exclusion also applies to3rd generation LQ

/

~

~~

~~

~ 01

01

Updating!


Indirect constraint: BS

CDF also looks at Bd

Background estimation: linear extrapolation from sidebands

Normalizing using B+- + K+

Rare decay, BR in SM is ~10-9

Loop diagrams with sparticles (or direct decay if RPV) enhance BR orders of magnitudeComplementary to other SUSY e and µ searches

Important at high tan


BS : Results

Previous limit:

hep-ph/0507233

Compatible with SM backgrounds:Bs Expect: 0.88±0.30 Observe: 1Bd Expect: 1.86±0.34 Observe: 2

Pink regions are excluded by either theory or experimentsGreen region is the WMAP preferred regionBlue dashed line is the Br(Bs) contourLight blue region excluded by old analysis

Limits with 780 pb-1:Br(Bs)<1.0×10-7 @ 95%CLBr(Bd )<3.0×10-8 @ 95%CL

SUSY with minimalSO(10)

NEW limit:


MSSM Higgs(es)

Analysis look for: l + hadronsFor m120 GeV:

expect 8.4, observe 11 events

All higgs searches working on updates for Summer

5 higgses to look for: h, H, A, H±

Charged: CDF looks for t H±bNeutral: enhanced production at large tan with h/H/A

hep-ex/0508051


Bump hunting: Z’Several BSM models predict new heavy gauge bosonsCDF searches for Z’ and W’New result: Z’ e+e- using 819 pb-1


Result: No signifiant bumpsLowest probability observed occurred in 52% of pseudo experimentsHighest mass event: Mee = 491 GeV/c² !

exclude MZ' <850 GeV

SM-Z'

Scan mass spectrum: 1 GeV steps

For each point: get P(bkg fluctuate data) in mass window given by calorimeter resolution


Large Extra Dimensions

SM backgrounds: Z+ jets, with Z, W+jets, QCD

Compactified extra dimensions (ADD model) with eff Planck scale MD:

M²Planck ~ RnMD²+n

Search for direct production of gravitons in gG or qG final states

Signature would be mono-jet + METET>150

Expect 265±30 eventsObs: 263

MET>120

MET


First look for anomously production of dilepton+X events (where X = large MET, jets, leptons, etc)

Can be signature for many models: Extra-D, SUSY, ...

Analysis investigating heavy quark model 3 heavy, down-type quarks Q i , decay to Z/H/WFinal state looks at lot like tt

Signal region: eµ + HT>400 GeV, 2 jets >50 GeV

Event expectation SM: 0.8 , QQ: 0.5, observe 0 Limit: (Q)<0.289 pb for m(Q)=300 GeV

Searching for heavy objects

Bjorken, Pakvasa, Tuan: hep-ph/0206116

HT= ET(e) + pT(µ) + ET(jets) + MET No overflows

-


Now looking for X Zwhere X = Z’, heavy q, neutralino ...

Signature would be high pT excessof events in Z mass window

(66 Mll 116 GeV/c²)

No observed excess on high pT tail for ee or µµ

More limits on heavy quarks: (Q) <0.17 pb @ 95% CL m(Q) = 300 GeV

and more to come ...

CDF Run II Preliminary (305 pb-1)


Diphoton + e//Several models predict diphoton signatures: Gauge mediated SUSY models,

excited leptons, fermiphobic higgs, ...Analysis inspired by Run I ee +MET event.

searches have huge backgrounds After requiring X almost no backgrounds Do not have to optimize analysis cuts to particular model

CDF has results on +e/µ and More analyses with +X on the way

Phys.Rev.D59.09002 (1999) by Toback et al.

~

q’


with 1020 pb-1

All photons pass same ID cutsBackground: fakes + real triphotonsExpectation: 1.9 events, observe 4

No significant excess is observedResults will set limits for several models

First case: l with 683 pb-1

Background: fakes or W / Z Expectation: 5.0 events, observe 2

(ET) > 13 GeV


LEP

excl

ud

ed

Conclusion- CDF and the Tevatron are in great shape!

- Results are pouring in, many more in the pipeline

- No sign of the New Physics yet

More analyses and more data for Summer could take us from great limits to great discovery(ies)!

Higgs sensitivity for Run II:

8 fb-1: exclude Higgs up to mass of 135 GeV

4 fb-1: exclude Higgs up to ~125 GeV


We know it is out there !

Backup


Vector Leptoquarks (322 pb-1)

Assuming 3rd gen VLQ decays to b+ - signature: lepton+MET+h+di-jet

Cut on: HT=pT(l)+pT(tau)+pT(jets)+MET > 400 GeV/c

New limit: mass 368 GeV/c2

assuming Br(VLQ3 b) = 100%.


Look in the Bs and Bd Signal Window

LR > 0.99

CMU-CMU Channel: Expect Observed ProbBs 0.88±0.30 1 67%Bd 1.86±0.34 2 63%

CMU-CMX Channel: Expect Observed ProbBs 0.39±0.21 0 68%Bd 0.59±0.21 0 55%


High pt Z’s


High mass ee event

run: 202771, event: 8309309

central-central

Mee = 491 GeV/c2


More Z’ Other analysis also exploring angular information: Z’ would interfere with Z/ look for change in expected shape of cos(*) for Mee > 200 GeV.Observation: 120 events, 115±19 expected similar mass limit with 450 pb-1

Testing angular shape

hep-ex/0602045

angle(incomming quarks, electrons)cos(*) in Colling-Soper frameminimize ambiguity in incomming q Pt

qq

e

e


New top mass and the MSSM

Plot from: http://quark.phy.bnl.gov/~heinemey/uni/plots/


More on MSSM higgs

•Br(bb)~90%

• gg,bbbb: need to overcome large QCD BG

•Br()~10%

• gg,bb overcome much smaller SM BG

Projection:


More plots from LS


CDF Trigger System• Rate of incoming events:

– Every 396 ns• Design specs: maximum

rate of accepting events:– L1: 50 kHz– L2: 300 Hz– L3: 30 Hz

• L2 currently is the bottleneck – Exceeded design specs to

operate at 380 Hz


Shutdown 2006

Detectors:Various maintenance and repairs +

CDF: Final Run II b upgrades: New TDC’s, upgrades to tracktriggers and hardware event builder.

D0: Add innermost Si layer + upgrades to track and calorimetertriggers

We are currently in a long showdown for maintenance of TeVExpected duration: March- June

Plenty of time

On trackPotentially tricky


Tagging B-jetsTagging B-jetsTagging jets with the SecVtx algorithm is a powerful way of selecting b-jets

Jet is tagged:• decay length Lxy/Lxy > 7• Lxy>0 identifies real heavy flavor jet

Tagged jet

Prim. vertex

2nd vertexLxy>0

• Currently using the tight tagger

• Development of a “forward b-jet tagging” is in progress to increase acceptance

• Mistag rate is ~1%

–Double-sided silicon microstrips: 800k channels!

–r ~1.5 cm out to ~50 cm


Jet reconstruction Final state partons are revealed through collimated flows of hadrons called jets

Need to have common and unambiguous definition used for theory and experiments. Jet reconstruction algorithms: - infrared and collinear safe - jet direction = parent parton direction

Two main types of jet algorithms:- Cone Algorithm JETCLU (Run I like) and MIDPOINT - KT algorithm

Measurements at hadron level Theory prediction parton level


Conversion removal SF


• COT Aging - Fully Recovered– Aging due to hydrocarbons

coating sense wires– Fixed by adding Oxygen– Fully recovered May 2004– 99.7% working!

• Silicon detector lifetime is a complex issue involving

• ~93% powered; ~84% working + 4% recoverable in offline

• Secondary vertex trigger requires 4 layers: 21 out of 24 wedges

COT Gain vs. Time

Jan.2002 Aug.2005

May 2004

Lifetime 0 10 fb-1 20 fb-1 30 fb-1 40

Predicted Silicon Lifetime

8 fb-1


Electron CoolingRecycler: 3.3 km in circumferenceStore antiprotons at 8 GeVMix pbars with 4.3 GeV electron beam reduce longitudinal emittance(Coulomb scattering until thermal equilibrium)


Higgs limit from D0


• Rp (R-parity) conserving– Lightest Supersymmetric Particle (LSP) is stable, escapes

detector (undetected)– Results in large ET

Miss

• striking exp. Signature• (Rp violating signatures)

– Often include lepton flavor violating decaysBreaking Models:• mSugra: supergravity-inspired

– Best-studied model, 5 parameters

• GMSB-motivated signatures– LSP: Gravitino, various next-LSP (NLSP)

• Experimentally: photons!• Run 1 CDF eET

Miss

• AMSB-motivated signatures– Long-lived particles, soft pions– Very hard at hadron colliders

G~~01

120 , , , tan ,sign( )m m A

0 0 122 1 1

122 0.8gm m m m m

sLBPR 2)(3)1(

2222~

2~

2~

2~

2~ )cot(4)(

2

12,1

ttttttt AmmmmmmRLRL

Lightest squark:

)tanhigh(~

),tanlow(~11 bt


e+, pT = 41 GeV

MET, 45 GeV

CDF Trilepton events

CMIOMET

CMUP

CMX

Mass OS1 41.6 GeV

Mass OS2 27.0 GeV

Jet ET = 50 GeVpT = 4 GeV

e-, pT = 12 GeV

searches for new physics with cdf else lytken, purdue university

Documents

conversions slide

e coverage

met jets

sm background

tevatron pp collider

purdue university slide

majorana particles leptons

outline o introduction