Xxxiv international meeting on fundamental physics
Download
1 / 38

XXXIV International Meeting on Fundamental Physics - PowerPoint PPT Presentation


  • 91 Views
  • Uploaded on

Physics at the Tevatron. XXXIV International Meeting on Fundamental Physics. From HERA and the TEVATRON to the LHC. Rick Field University of Florida ( for the CDF & D0 Collaborations ). Real Colegio Maria Cristina, El Escorial, Spain. 3 nd Lecture

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' XXXIV International Meeting on Fundamental Physics' - von


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Xxxiv international meeting on fundamental physics

Physics at the Tevatron

XXXIV International Meeting on Fundamental Physics

From HERA and the TEVATRON

to the LHC

Rick Field

University of Florida

(for the CDF & D0 Collaborations)

Real Colegio Maria Cristina, El Escorial, Spain

3nd Lecture

Photons, Bosons, and Jets at the Tevatron

CDF Run 2

Rick Field – Florida/CDF/CMS


Photons bosons and jets at the tevatron
Photons, Bosons, and Jets at the Tevatron

  • The Direct Photon Cross-Section.

Some Cross Sections Measured at the Tevatron

  • The g + Heavy Quark Cross-Section.

and comparisons with theory!

  • The g + g Cross-Section.

  • The Z-Boson Cross-Section.

  • The W-Boson Cross-Section.

  • The W+Jets, Z+Jets, and Z+b-Jet Cross-Sections.

  • The W+g and Z+g Cross-Sections.

  • The W+W Cross-Section.

  • The Higgs → W+W Cross-Section.

  • H → W+W with 100 times more data!

  • The W+Z and Z+Z Cross-Sections.

  • The Inclusive Jet and DiJet Cross-Sections.

Rick Field – Florida/CDF/CMS


The direct photon cross section

q

g

q

The Direct Photon Cross-Section

  • DØ uses a neural network (NN) with track isolation and calorimeter shower shape variables to separate direct photons from background photons and p0’s!

Note rise at low pT!

Highest pT(g) is 442 GeV/c

(3 events above 300 GeV/c not displayed)!

Rick Field – Florida/CDF/CMS


G b c cross sections cdf
g + b/c Cross Sections (CDF)

L = 67 pb-1

  • b/c-quark tag based on displaced vertices. Secondary vertex mass discriminates flavor.

Rick Field – Florida/CDF/CMS


G b c cross sections cdf1
g + b/c Cross Sections (CDF)

PYTHIA Tune A!

L = 67 pb-1

g + b

g + c

  • PYTHIA Tune A correctly predicts the relative amount of u, d, s, c, b quarks within the photon events.

ET(g) > 25 GeV

Rick Field – Florida/CDF/CMS


G g cross section cdf
g + g Cross Section (CDF)

L = 207 pb-1

QCD g + g

g + gDf

g + g mass

  • Di-Photon cross section with 207 pb-1 of Run 2 data compared with next-to-leading order QCD predictions from DIPHOX and ResBos.

Rick Field – Florida/CDF/CMS


Z boson cross section cdf
Z-boson Cross Section (CDF)

L = 72 pb-1

QCDDrell-Yan

  • Impressive agreement between experiment and NNLO theory (Stirling, van Neerven)!

Rick Field – Florida/CDF/CMS


Z boson cross section cdf1
Z-boson Cross Section (CDF)

L = 337 pb-1

  • Impressive agreement between experiment and NNLO theory (Stirling, van Neerven)!

Rick Field – Florida/CDF/CMS


The z tt cross section cdf

Channel for Z→ττ: electron + isolated track

One t decays to an electron: τ→e+X (ET(e)> 10 GeV) .

One t decays to hadrons: τ → h+X (pT > 15GeV/c).

Remove Drell-Yan e+e- and apply event topology cuts for non-Z background.

Signal

cone

Isolation

cone

The Z→tt Cross Section (CDF)

  • Taus are difficult to reconstruct at hadron colliders

    • Exploit event topology to suppress backgrounds (QCD & W+jet).

    • Measurement of cross section important for Higgs and SUSY analyses.

  • CDF strategy of hadronic τ reconstruction:

    • Study charged tracks define signal and isolation cone (isolation = require no tracks in isolation cone).

    • Use hadronic calorimeter clusters (to suppress electron background).

    • π0 detected by the CES detector and required to be in the signal cone.

  • CES: resolution 2-3mm, proportional strip/wire drift chamber at 6X0 of EM calorimeter.

New

Rick Field – Florida/CDF/CMS


The z tt cross section cdf1

1 and 3 tracks,

opposite sign

same sign,

opposite sign

The Z→tt Cross Section (CDF)

New

  • CDF Z→ττ (350 pb-1): 316 Z→ττ candidates.

  • Novel method for background estimation: main contribution QCD.

  • τ identification efficiency ~60% with uncertainty about 3%!

Rick Field – Florida/CDF/CMS


Higgs tt search cdf
Higgs → tt Search (CDF)

events

New

140 GeV Higgs Signal!

1 event

  • Data mass distribution agrees with SM expectation:

    • MH > 120 GeV: 8.4±0.9 expected, 11 observed.

  • Fit mass distribution for Higgs Signal (MSSM scenario):

    • Exclude 140 GeV Higgs at 95% C.L.

    • Upper limit on cross section times branching ratio.

Rick Field – Florida/CDF/CMS


W boson cross section cdf
W-boson Cross Section (CDF)

W Acceptance

  • Extend electron coverage to the forward region (1.2 < |h| < 2.8)!

48,144 W candidates ~4.5% background overall efficiency of signal ~7%

Rick Field – Florida/CDF/CMS


20 years of measuring w z
20 Years of Measuring W & Z

Rick Field – Florida/CDF/CMS


W jets production cdf
W+Jets Production (CDF)

  • Background to Top and Higgs Physics.

  • Testing ground for pQCD in multi-jet environment.

L = 320 pb-1

  • Restrict sW :

    • W → e n, |he|< 1.1.

  • JETCLU jets (R=0.4):

    • ETjets>15 GeV, |hjet|< 2.

  • Uncertainties dominated by background subtraction and Jet Energy Scale.

LO predictions normalized to data integrated cross sections:

 Shape comparison only!

Rick Field – Florida/CDF/CMS


W jets production cdf1
W+Jets Production (CDF)

  • Important to study distributions and topological structure of W + Jets!

di-jet DR distribution in the W+ ≥2 jet

di-jet invariant mass distribution in the W+ ≥2 jet

LO predictions normalized to data integrated cross sections:

 Shape comparison only!

More exhaustive comparisons expected soon!!!

Rick Field – Florida/CDF/CMS


Z jets production d
Z+Jets Production (DØ)

  • Same physics as W + jets s(Z) ~ s(W)/10, but Z→e+e- cleaner.

  • Central electrons (|h|<1.1).

  • MidPoint jets: (R = 0.5, pT > 20 GeV/c, |yjet|<2.5).

L = 343 pb-1

PT distribution of the nth jet

Z+j

MCFM: NLO for Z+1p or Z+2p  good description of the measured cross sections.

ME + PS: with MADGRAPH tree level process up to 3 partons  reproduce shape of Njet distributions (Pythia used for PS).

Z+2j

Z+3j

Rick Field – Florida/CDF/CMS


Z b jet production cdf d
Z + b-Jet Production (CDF & DØ)

  • Important background for new physics!

  • Leptonic decays for the Z.

  • Z associated with jets.

  • CDF: JETCLU, D0: MidPoint:

  • R = 0.7, |hjet| < 1.5, ET >20 GeV

  • Look for tagged jets in Z events.

L = 335 pb-1

L = 180 pb-1

Extract fraction of b-tagged jets from secondary vertex mass distribution: NO assumption on the charm content.

CDF

Assumption on the charm content from theoretical prediction: Nc=1.69Nb.

Agreement with NLO prediction:

Rick Field – Florida/CDF/CMS


W g cross sections cdf
W + g Cross Sections (CDF)

ET(g) > 7 GeV

R(lg) > 0.7

Rick Field – Florida/CDF/CMS


Z g cross sections cdf
Z + g Cross Sections (CDF)

Note: (W)/(Z) ≈ 4

while (W)/(Z) ≈ 11

ET(g) > 7 GeV

R(lg) > 0.7

Rick Field – Florida/CDF/CMS


The w w cross section
The W+W Cross-Section

Campbell & Ellis 1999

Rick Field – Florida/CDF/CMS


The w w cross section cdf
The W+W Cross-Section (CDF)

L = 825 pb-1

We are beginning to study the details of

Di-Boson production at the Tevatron!

  • WW→dileptons + MET

  • Two leptons pT > 20 GeV/c.

  • Z veto.

  • MET > 20 GeV.

  • Zero jets with ET>15 GeV and |h|<2.5.

New

Observe 95 events with 37.2 background!

Missing ET!

Lepton-Pair Mass!

ET Sum!

Rick Field – Florida/CDF/CMS


The z w z z cross sections

W+Z → trileptons + MET

The Z+W, Z+Z Cross Sections

Observe 2 events with a background of 0.9±0.2!

Upper Limits

Rick Field – Florida/CDF/CMS


Di bosons at the tevatron
Di-Bosons at the Tevatron

W

We are getting closer to the Higgs!

Z

W+g

Z+g

W+W

W+Z

Rick Field – Florida/CDF/CMS


Generic squark and gluino search
Generic Squark and Gluino Search

  • Selection:

    • 3 jets with ET>125 GeV, 75 GeV and 25 GeV.

    • Missing ET>165 GeV.

    • HT=∑ jet ET > 350 GeV.

    • Missing ET not along a jet direction:

      • Avoid jet mismeasurements.

  • Background:

    • W/Z+jets with Wl or Z.

    • Top.

    • QCD multijets:

      • Mismeasured jet energies lead to missing ET.

PYTHIA Tune A

  • Observe: 3, Expect: 4.1±1.5.

Rick Field – Florida/CDF/CMS


Future higgs susy searches
Future Higgs & SUSY Searches

  • CDF and Tevatron running great!

    • Often world’s best constraints.

    • Many searches on SUSY, Higgs and other new particles.

  • Most currewnt analyses based on up to 350 pb-1:

    • We will analyze 1 fb-1 by summer 2006.

    • Anticipate 4.4 - 8.6 fb-1 by 2009.

  • If Tevatron finds no new physics it will provide further important constraints:

    • And hopefully LHC will then do the job!

If we find something the

real fun starts: What Is It?

Rick Field – Florida/CDF/CMS


Jets at tevatron

“Theory Jets”

“Tevatron Jets”

Jets at Tevatron

  • Experimental Jets: The study of “real” jets requires a “jet algorithm” and the different algorithms correspond to different observables and give different results!

Next-to-leading order parton level calculation

0, 1, 2, or 3 partons!

  • Experimental Jets: The study of “real” jets requires a good understanding of the calorimeter response!

  • Experimental Jets: To compare with NLO parton level (and measure structure functions) requires a good understanding of the “underlying event”!

Rick Field – Florida/CDF/CMS


Jet corrections
Jet Corrections

  • Calorimeter Jets:

    • We measure “jets” at the “hadron level” in the calorimeter.

    • We certainly want to correct the “jets” for the detector resolution and effieciency.

    • Also, we must correct the “jets” for “pile-up”.

    • Must correct what we measure back to the true “particle level” jets!

  • Particle Level Jets:

    • Do we want to make further model dependent corrections?

    • Do we want to try and subtract the “underlying event” from the “particle level” jets.

    • This cannot really be done, but if you trust the Monte-Carlo models modeling of the “underlying event” you can try and do it by using the Monte-Carlo models (use PYTHIA Tune A).

  • Parton Level Jets:

    • Do we want to use our data to try and extrapolate back to the parton level?

    • This also cannot really be done, but again if you trust the Monte-Carlo models you can try and do it by using the Monte-Carlo models.

The “underlying event” consists of hard initial & final-state radiation plus the “beam-beam remnants” and possible multiple parton interactions.

Rick Field – Florida/CDF/CMS


Inclusive jet cross section d
Inclusive Jet Cross Section (DØ )

  • MidPoint Cone Algorithm (R = 0.7, fmerge = 0.5)

  • L= 378 pb-1

  • Two rapidity bins

  • Highest PT jet is 630 GeV/c

  • Compared with NLO QCD (JetRad, No Rsep)

Note that DØ does not make any

corrections for hadronization

and the “underlying event”!?

They compare the NLO parton level

directly to their hadron level data!

Log-Log Scale!

Rick Field – Florida/CDF/CMS


Di jet cross section d
Di-Jet Cross Section (DØ)

  • MidPoint Cone Algorithm (R = 0.7, fmerge = 0.5)

  • L= 143 pb-1

  • |yjet| < 0.5

  • Compared with NLO QCD (JetRad, Rsep = 1.3)

  • Update expected soon!

Rick Field – Florida/CDF/CMS


Inclusive jet cross section cdf

CTEQ4M PDFsCTEQ4HJ PDFs

Run I CDF Inclusive Jet Data(Statistical Errors Only)JetClu RCONE=0.7 0.1<||<0.7R=F=ET /2 RSEP=1.3

CTEQ4HJ

CTEQ4M

Inclusive Jet Cross Section (CDF)

  • Run 1 showed a possible excess at large jet ET (see below).

  • This resulted in new PDF’s with more gluons at large x.

  • The Run 2 data are consistent with the new structure functions (CTEQ6.1M).

Rick Field – Florida/CDF/CMS


Inclusive jet cross section cdf1
Inclusive Jet Cross Section (CDF)

  • MidPoint Cone Algorithm (R = 0.7, fmerge = 0.75)

  • Data corrected to the hadron level

  • L= 1.04 fb-1

  • 0.1 < |yjet| < 0.7

  • Compared with NLO QCD (JetRad, Rsep = 1.3)

Sensitive to UE + hadronization effects for PT < 200 GeV/c!

Rick Field – Florida/CDF/CMS


K t algorithm
KT Algorithm

  • kT Algorithm:

    • Cluster together calorimeter towers by their kT proximity.

    • Infrared and collinear safe at all orders of pQCD.

    • No splitting and merging.

    • No ad hoc Rsep parameter necessary to compare with parton level.

    • Every parton, particle, or tower is assigned to a “jet”.

    • No biases from seed towers.

    • Favored algorithm in e+e- annihilations!

KT Algorithm

Will the KT algorithm be effective in the collider environment where there is an “underlying event”?

Raw Jet ET = 533 GeV

Raw Jet ET = 618 GeV

CDF Run 2

Only towers with ET > 0.5 GeV are shown

Rick Field – Florida/CDF/CMS


K t inclusive jet cross section cdf
KT Inclusive Jet Cross Section (CDF)

  • KT Algorithm (D = 0.7)

  • Data corrected to the hadron level

  • L= 385 pb-1

  • 0.1 < |yjet| < 0.7

  • Compared with NLO QCD (JetRad) corrected to the hadron level.

Sensitive to UE + hadronization effects for PT < 300 GeV/c!

Rick Field – Florida/CDF/CMS


Hadronization and underlying event corrections

MidPoint Cone Algorithm (R = 0.7)

Hadronization and “Underlying Event” Corrections

  • Compare the hadronization and “underlying event” corrections for th KT algorithm (D = 0.7) and the MidPoint algorithm (R = 0.7)!

Note that DØ does not make any

corrections for hadronization

and the “underlying event”!?

  • We see that the KT algorithm (D = 0.7) is slightly more sensitive to the underlying event than the cone algorithm (R = 0.7), but with a good model of the “underlying event” both cross sections can be measured at the Tevatrun!

The KT algorithm is slightly more sensitive to the “underlying event”!

Rick Field – Florida/CDF/CMS


K t inclusive jet cross section cdf1
KT Inclusive Jet Cross Section (CDF)

NLO parton level theory corrected to the “particle level”!

D = 0.5

D = 1.0

Data at the “particle level”!

7

8

7

Correction factors

applied to NLO theory!

Corrections increase as D increases!

Rick Field – Florida/CDF/CMS


High x gluon pdf

from Run I

Big uncertainty for high-x gluon PDF!

High x Gluon PDF

  • Forward jets measurements put constraints on the high x gluon distribution!

Uncertainty on gluon PDF (from CTEQ6)

x

Rick Field – Florida/CDF/CMS


K t inclusive jet cross section cdf2
KT Inclusive Jet Cross Section (CDF)

  • KT Algorithm (D = 0.7).

  • Data corrected to the hadron level.

  • L = 385 pb-1.

  • Five rapidity regions:

    • |yjet| < 0.1

    • 0.1 < |yjet| < 0.7

    • 0.7 < |yjet| < 1.1

    • 1.1 < |yjet| < 1.6

    • 1.6 < |yjet| < 2.1

  • Compared with NLO QCD (JetRad) with CTEQ6.1

Excellent agreement over all rapidity ranges!

Rick Field – Florida/CDF/CMS


Jet jet correlations d

Df Jet#1-Jet#2

Jet#1-Jet#2 Df Distribution

Jet-Jet Correlations (DØ)

  • MidPoint Cone Algorithm (R = 0.7, fmerge = 0.5)

  • L= 150 pb-1 (Phys. Rev. Lett. 94 221801 (2005))

  • Data/NLO agreement good. Data/HERWIG agreement good.

  • Data/PYTHIA agreement good provided PARP(67) = 1.0→4.0 (i.e. like Tune A, best fit 2.5).

Rick Field – Florida/CDF/CMS


ad