Recent Results from the Tevatron Alison Lister UC Davis

EPFL seminar 29th October 2007 Alison Lister, UC Davis 1

Outline

• • • • •

The Tevatron and Experiments

 CDF XFT trigger Upgrade

‘Bread and Butter’ Physics

 Precision measurements of SM processes

The ‘Known Knowns’

 Recent observations

The ‘Unknown Knowns’

 SM Higgs Searches

The ‘Unknown Unknowns’

 Beyond SM Searches EPFL seminar 29th October 2007 Alison Lister, UC Davis 2

• •

Tevatron Performance

Many improvements over last year

•

More pbars, more reliably

 

Monthly integrated luminosity increased 25



Peak luminosity increased 180e30



45 pb 292e30 cm -2 s -1 -1

Expect ~6-7 fb

-1

by Oct. ‘09 Thanks to the Accelerator Division!

1500 pb -1 750 pb -1 2006 Design 2007 2005 Base 2004 2003

EPFL seminar 29th October 2007 3

Symmetric around beam axis Front-back symmetric ~100 tons

CDF II

1.4 Tesla solenoid Muon coverage up to |  | ~ 1.1

EPFL seminar 29th October 2007 Dedicated silicon detector for secondary vertex tagging Electron reconstruction up to |  | ~ 2.8

Alison Lister, UC Davis 4

Symmetric around beam axis Front-back symmetric

DØ II

Solenoid + Toroid magnets Liquid argon compensating calorimeter June 2006: Start of Run IIb First data with L0 silicon detector EPFL seminar 29th October 2007 Alison Lister, UC Davis 5

CDF + D Ø

• Integrated luminosity   ~3.3 fb -1 by July 2007 About half-way to expected data size 3.3 fb -1 2.7 fb -1 Took >2 years of collisions to get to stable high efficiency EPFL seminar 29th October 2007 • Data taking efficiency  CDF + DØ ~87% • Starting/stopping runs • • DAQ/hardware problems Trigger dead-time  ~80% of delivered luminosity is used in analyses Alison Lister, UC Davis 6

CDF Trigger Upgrades

• • Peak luminosity increasing   Close to design luminosity Record is 282e30 Trigger rates grow rapidly with instantaneous luminosity  Mostly due to ‘fakes’ and not real physics CMX inclusive high p T muons default • • • 300e30 CDF 3-tier trigger system limited by bandwidth at L2 Adding pre-scales to triggers to keep rates down compromises physics goals Series of trigger upgrades to keep high efficiency while reducing rates EPFL seminar 29th October 2007 Alison Lister, UC Davis 7

XFT Trigger Upgrade

• • COT (Central Outer Tracker)   4 axial superlayers 4 stereo superlayers eXtremely Fast Tracker (XFT)   Track triggering system Affects ~80% of all CDF physics + Z in SL7 Real tracks Reject Fakes !

Z in SL5 EPFL seminar 29th October 2007 + • • SL7 (stereo)  pixel (SL7) SL6 (axial) SL5 (stereo) SL4 (axial) SL3 (stereo)  pixel (SL5) SL5 has opposite stereo angle  pixel (SL3) Before upgrades  Only using axial superlayers XFT L1 upgrade  Confirm axial track passes through stereo layers and rough alignment of track in 3D  Gain factor 3-4 in rate

Commissioned Oct 2006

Alison Lister, UC Davis 8

XFT L2 Upgrade

• Use full stereo information to reconstruct tracks in 3D and combine with information from outer detector components • • • Rate reduction factor 4 - 3.4

Efficiency for well reconstructed muons ~99% Combination of L1 and L2 XFT upgrades should take us safely beyond the Tevatron design luminosity default L1 confirmed L2 pointing Fermilab Engineer S.Holm about the system: “The most difficult firmware in my 25 year experience” EPFL seminar 29th October 2007 Commissioning this autumn Alison Lister, UC Davis 9

Latest Results for LP07

• • • • 51 (42) new results from CDF (D Ø) shown at LP07 conference 31 from CDF using full data up to April 2007 (2.2 fb -1 ) All areas covered from precision measurements of the W mass to MSSM Higgs searches Many searches using “state of the art” techniques     Neural Networks Matrix Element Decision Trees … EPFL seminar 29th October 2007 Alison Lister, UC Davis 10

Tevatron Sensitivities

• 1st Physics [few 100 pb -1 ]  Heavy flavor physics, inclusive W/Z, re-establish top More data Better understanding of ‘backgrounds’ • Now [1-2 fb -1 ]  Precision M t , B s -Mixing, Top properties, Observation of rare processes ~9 orders of magnitude • Looking Ahead [? fb -1 ]   Even rarer processes, New Physics searches, Higgs ‘The’ unexpected The focus is now to uncover the unknown EPFL seminar 29th October 2007 Alison Lister, UC Davis 11

‘Bread and Butter’ Physics

EPFL seminar 29th October 2007 Alison Lister, UC Davis 12

W+ c-jet Cross-Section

Important background for ttbar and Higgs 1.0 fb -1 Can constrain s-quark PDF • • Select W + jets sample from lepton + jets final state W + c-jet sample   Jet tagged with muon • p T >20 GeV/c and |  |<2.5

W →l  (l=e, μ,  where  decays leptonically) • Lepton p T >20 GeV/c and Missing transverse energy > 20 GeV  Exploit correlation between charges of leptons • • Background: same sign Signal: opposite sign W+c-jet fraction = 0.071 ± 0.017

In agreement with LO theoretical predictions EPFL seminar 29th October 2007 Alison Lister, UC Davis 13

CP Violation in B

± →

J/



K

± 1.6 fb -1 • • • • • Looking for charge asymmetry in b → c cbar bbar and conjugate Asymmetry sensitive to new physics Use kaon charge tag Exploit polarity reversal of magnets to remove detector bias Need careful modeling of kaon asymmetry due to different inelastic cross-sections in detector  K + N →  has no K N counterpart • • Unbinned fit to signal Likelihood fit parametrisastion of backgrounds A CP (B + →J/  K + )= 0.0067

± 0.0074 (stat.

) ± 0.0026 (syst) Factor 2 better precision than world average Consistent with SM predictions of ~1% EPFL seminar 29th October 2007 Alison Lister, UC Davis 14

W Mass

• • • Template fit to    Transverse Mass Transverse Momentum Transverse Missing Energy Using their own fast MC simulation Data driven shape constraints 0.2 fb -1 Momentum scale calibration • • 63 964 W →e  51 128 W →μ  events events EPFL seminar 29th October 2007 M W = 80413 ± 34 (stat) ± 34 (syst) MeV/c 2 Alison Lister, UC Davis 15

Top Mass

1.2 fb -1 • • • • Many methods with improvements and more data Some new ideas  e.g measuring the mass using cross-section constraint In dilepton channel (l=e, μ) Under-constrained system solved using ttbar longitudinal momentum • • • Replacing statistical with theoretical uncertainties Sensitive to kinematics of events as well as number of events 70 events pass all selection criteria M t =170.7 +4.2-3.9 (stat.) ± EPFL seminar 29th October 2007 2.6 (syst.) ± GeV/c 2 Alison Lister, UC Davis 2.4 (theory) 16

• •

Top Mass

March 2007 This autumn big CDF publication push for all analyses with 2.2 fb -1 Expect ~10 new measurements since latest combination 1.1-1.8 fb -1 EPFL seminar 29th October 2007 Is it looking less and less SM-like or is that just me?

DØ-CDF Joint Systematics Effort Underway!

New combinations will follow… Alison Lister, UC Davis 17

Finding the ‘Known Knowns’

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Diboson Results

SM t-channel Triple Gauge Couplings?

s-channel EPFL seminar 29th October 2007 Alison Lister, UC Davis 19

•

WZ Production

WZ →l’  ll    3 isolated lepton • e, μ,  →e,μ • One > 25 Gev, other 2 > 10 GeV Missing E T (for the  ) > 25 GeV Clean signal but BR only 1.8% 1.9 fb -1 Lepton composition (t=track) EPFL seminar 29th October 2007 • • 2 leptons  opposite sign, same flavour, Z mass window Fit using log likelihood ratio  (WZ) = 4.1 +1.3

-1.0

(stat) ± 0.2(syst) 0.3(lumi) In agreement with NLO prediction ± Alison Lister, UC Davis 20

WWZ Couplings

• • Anomalous coupling limits set using p T distribution of Z-boson Fit data using binned log likelihood to 3 parameters  ,  g and  for 2 different values of  (1.5 and 2.0 TeV) 1.9 fb -1 NLO MCFM Consistent with SM NLO without triple gauge coupling EPFL seminar 29th October 2007 Alison Lister, UC Davis 21

 b •

Direct Observation

Many new baryon discoveries this past year 1.3 fb -1 •  b (dsb) one quark from each generation • Fully reconstruct exclusive decay  Sign of charge of tracks • •   Reconstructed displaced vertices Masses and impact parameter resolution of reconstructed vertices  Angular separation between tracks  Minimum p T Use  + requirements for background studies  wrong-sign Interpretation of peak as  b using unbinned likelihood Peak: 5.5

 significance M(  b ) =5.774 ± 0.011(stat) ± 0.015(syst) EPFL seminar 29th October 2007 Alison Lister, UC Davis 22

Evidence for Single Top

0.9 fb -1 • • • • SM:  ~ 3 pb and rate  |V tb | 2 Combine 3 analyses    Decision Tree Matrix Element Method Bayesian Neural Network Best Linear Unbiased Estimate Assume SM ratio between s- and t channel cross-sections Boosted Decision Trees Combined: 3.6

 significance Multivariate techniques can coax signal out from large backgrounds EPFL seminar 29th October 2007 Alison Lister, UC Davis 23

Trying to find the ‘Unknown Knowns’

EPFL seminar 29th October 2007 Alison Lister, UC Davis 24

SM Higgs Production + Decay

• • Direct production gg →H   Highest Production rate Largest background Associated production ZH/WH  Leptonic vector boson decay helps for triggering and signal extraction • • • Decay modes Low Mass (M  H <135 GeV/c H →bb mode dominates 2 ) High Mass (135

SM H → WW

*

→ l



l

 • • • Most sensitive channel for high mass Higgs 2 leptons: e,  ,  → e,   Must have opposite signs Using Matrix Element Method  Event probability density from LO matrix elements from MCFM 1.9 fb -1 EPFL seminar 29th October 2007 • Data compared to NNLL calculation for different mass hypotheses Limit at 2.0*  SM for M H =160 GeV/c 2 Looks like CDF was lucky this time… Alison Lister, UC Davis 26

SM Higgs Limits

0.9-1.9 fb -1 Run 1 0.1 fb -1 0.3-1.0 fb -1 1-2 fb -1

The Tevatron experiments are doing much better than √(∫ lumi)

EPFL seminar 29th October 2007 Alison Lister, UC Davis 27

SM Higgs Limits

0.9-1.9 fb -1 • Combining all limits from all channels as well as between CDF and D0 EPFL seminar 29th October 2007 Alison Lister, UC Davis 28

SM Higgs Limits

0.9-1.9 fb -1 • • Projections based on 2 x D0 results (for CDF + D0) Assuming better than √(∫ lumi)  Reducing systematics, increasing acceptance, including more channels (  ) EPFL seminar 29th October 2007 Alison Lister, UC Davis 29

Looking for the ‘Unknown Unknowns’

EPFL seminar 29th October 2007 Alison Lister, UC Davis 30

•

Deviations from SM

New CDF web page “Discovery Watch” (soon to be made public) EPFL seminar 29th October 2007 Alison Lister, UC Davis 31

SUSY + mSUGRA

• • SUSY is one of the more popular extensions to the SM mSUGRA   SUSY symmetry broken by gravity at GUT scale 5 parameters: m 0 , m 1/2 , tan  , A 0 , sign(µ) • • • Previous Tevatron squark/gluino searches using Jet and large MET  Mainly arising from decay of LSP High tan   Squarks decay to charginos and neutralinos  Final states with leptons Some models stau might be lightest lepton   Enhanced cross-section to taus Squarks lighter than gluinos EPFL seminar 29th October 2007 Alison Lister, UC Davis 32

SUSY: Squarks with Jet,

 h

, MET

• • • • 0.96 fb -1 ≥2 jets (∆  12 >165˚,E T >35 GeV, |  |<0.8) MET ≥ 175 GeV At least one isolated hadronically decaying  (E T >15 GeV, |  |< 2.5)  Separate  h from jets and electrons using loose cuts to NN outputs  HT = E T  + E T jet1 + E T jet2 ≥ 325 GeV • • • • • Main backgrounds: Z( →  )+jets, ttbar,W+jets  Modeled by ALPGEN+PYTHIA QCD negligible after selection  -decays simulated by TAUOLA Dominant systematic Jet Energy Scale 2 observed events EPFL seminar 29th October 2007 Alison Lister, UC Davis tan  = 15 A = -2m 0 µ<0 LEP chargino searches 33

t’ Search

• • • Massive 4 th generation top-like quark Predicted by some SUSY models (beautiful mirrors), Little Higgs Generic 4 th chiral generation allowed by EWK data; can accommodate a heavy Higgs (~500 GeV) without any other new particles QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.

0.76 fb -1 • • Looking for interesting events on the tails of distributions Analysis will be re-done with ~2.2 fb -1 making use of heavy flavour tagging to hopefully increase sensitivity

Exclude with 95% CL t

´

mass below 256 GeV/c

2 EPFL seminar 29th October 2007 Alison Lister, UC Davis 34

Couple of Strange Events…

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High Mass Resonances in ee

• • • Model independent search for high mass narrow resonances Scan Mass region 150-500 GeV/c 2 in 5 GeV/c 2 steps Assume narrow resonance  Model with Gaussian of width equal to detector resolution 0.9 fb -1

?

EPFL seminar 29th October 2007 • Fit distribution to background only and background + narrow resonance  Estimate probability of background giving  2 as large as largest deviation: 1.7% Excess around 240 GeV/c 2 Alison Lister, UC Davis 36

Model Independent Searches

0.9 fb -1 • VISTA    Model independent approach that looks at gross features of the data Sensitive to new large cross-section physics   Partitioning of events into exclusive final states • e,µ,  ,  ,jet,missing p T , … Global comparison to SM predictions from PYTHIA, MADEVENT and/or HERWIG 16’486 kinematic distributions from 344 exclusive final states • 409 distributions with deviation > 5  • None believed to have new physics interpretation EPFL seminar 29th October 2007 Alison Lister, UC Davis 37

SLEUTH

0.9 fb -1 • • • • • Quasi-model independent approach emphasizes the high Σp T tails Particularly sensitive to new electroweak scale physics Looks at one variable: Σp T for all final states Uses correction factors to SM predictions found by VISTA SLEUTH determines most interesting region of tail • • • • Same-sign e mu + 2 jets + MET final state 4 data events observed 0.71 SM events predicted 2.5 sigma effect (stat only) EPFL seminar 29th October 2007 Alison Lister, UC Davis 38

• • • • •

Status of the SM

Very rich and diverse physics program  “Looking in most nooks and crannies” Background understanding improving  Small systematic uncertainties in searches Experiments found many new processes expected by SM  Sensitive to beyond SM Higgs discovery at Tevatron looks much exciting than it did a year ago  New results expected in next year Model dependent and model independent searches showing “noise” above SM predictions but nothing concrete

We know something is out there but what and where?

EWK fit: M H <182 GeV/c 2 (incl. LEP direct exclusion) EPFL seminar 29th October 2007 Alison Lister, UC Davis 39

Backup Slides

EPFL seminar 29th October 2007 Alison Lister, UC Davis 40

• •

Evidence for ZZ

ZZ →llll and ZZ→ll  (l = e or  ) Systematics  Mostly dominated by cross-section uncertainty of back-ground processes   Drell-Yan the missing E T is dominant W+jets dominated by lepton fake rate 1.1-1.5 fb -1 Likelihood ratio plot for ll  Measured:  (ZZ) = 0.75 + 0.71

SM NLO:  (ZZ) = 1.4 ± - 0.54

0.1 pb pb Consistent with SM without triple gauge coupling EPFL seminar 29th October 2007 Alison Lister, UC Davis 41

1.1-2.2 fb -1

B Baryon Discoveries



b

 b  b EPFL seminar 29th October 2007 Alison Lister, UC Davis 42