1

ELECTROWEAK PHYSICS

Heidi Schellman – Northwestern University

2

What is not in this talk Results from previous years – except for context Top quark mass and single top production

Mousumi Datta The CKM matrix

Dave Hitlin and Tom Browder The MNS matrix

Bonnie Flemming The Higgs

Mark Kruse Weak boson production (QCD)

Don Lincoln These are arguably all electroweak measurements.

3

What’s left Precision measurements

of electroweak couplings and mass The W mass Measurements of the

weak mixing angle. Very rare electroweak

processes. Diboson production

And the future…

Predictions of GSW theory

A neutral Z0 boson

W, Z0 and g couplings and masses have tightly constrained relations: MW/MZ = cos qw e = g sin qw

Symmetry breaking would like a Higgs Field

There should be at least one physical scalar Higgs boson left over to observe

Couplings and Masses Higgs Field

4

Why constants aren’t constant

This is an electron

This is a closeup of an electron

This is a real closeup of an electron.

Properties depend on distance/energy scale and properties of all other particles which can couple

5

Renormalization

Relations of masses and angles6

Δr1sinθ1

FG2πα

WMW

Dr ∞ Mt 2 Dr ∞ logMH

Measure qW, predict MWConsistency of indirect and direct measures?

LEP/SLD measurements of MZ, MW ,sin2qw

LEP/SLD e+e-

Measure Z mass 91.1876+/- 0.0021 GeV Measure Z weak couplings to all fermions by

measuring g*/Z interference and the Z width. Precise measurement of sin2qw Measure the W mass with 0.033 GeV resolution

Tevatron - hadron-hadron scattering Forward backward asymmetry AFB MW

7

8

Z’s at hadron colliders

LEP recorded 17M Z events eeff of Which 1.7M were to Leptons (including tau’s)

Tevatron now has reconstructed ~ 0.2-0.6M events x 2 channels (ee+mm) x 2 expts (D0/CDF)~ up to 1.6 M Zll already depending on cuts.Close to LEP statistics! LHC experiments expected to have much higher cross

sections with ~2 M Z ll in the first fb-1 !

35,626 events qq ee

9

Signatures uu + dd Z ll

Tevatron is mainly valence-valence scattering.

LHC is mainly valence-sea scattering and must choose boosted Z’s to tell valence from sea. PDF’s will be a

dominant uncertainty.

10

Current measurement from D0

Junjie Zhu

AFB

qqZ/g* eesin2qw=0.2326±0.0018(stat)

±0.006(syst)Phys. Rev. Lett. 101, 191801 (2008),   arXiv.org:0804.3220

Trang HoangFriday EWK IIII

11

AFB measurements

Future measurements from the Tevatron and the LHC are expected to reach 0.0005 or better accuracy. The limiting factor is probably PDF’s.

12

W mass from CDF - 2007

Both muon and electron channelsScale set by the CDF trackerAbsolute measurement of MW

Chris HaysTuesday EWK I

13

New W mass measurement 1 fb-1 of data taken 2002-2006 ~ 18,725 Z and 499,830 W candidates in the

electron channel only. Use data to determine corrections wherever

possible Blind analysis – central mass value hidden until

everything has been reviewed. Because Zee is the main calibration, this is

effectively a MW/MZ measurement – many physics effects cancel.

NOT very correlated with the CDF measurement!

Jyotsna OstaTuesdayEWK I

W boson mass - W -> en mode

Cannot measure n or W momentum along beam Use variables defined in transverse plane

pTe

ET = inferred neutrino pTn

mT = √2 pTe ET (1-cosDf)

Only electrons with |h| < 1.1 used

ET

pTe

15

Crosschecks

Check everything… Results: Z e e data

16

pT(e)

GeVGeV

GeVGeV

uT

m(ee)

pT(ee)

Good agreement between parameterized MC and collider data.

DØ Preliminary, 1 fb-1

DØ Preliminary, 1 fb-1

DØ Preliminary, 1 fb-1

DØ Preliminary, 1 fb-1

17

W boson mass

Fit data to simulated distributions by varying mW Hid the fitted W mass

value until all control plots were OK

mT

Also fit pTe, pT

n

mW = 80.401 ± 0.023± 0.037 GeV

19

W boson mass

Limited by Z->ee statistics, will improve with more data

mW(mT) = 80.401 ± 0.023 (stat) ± 0.037 (syst) GeV mW(pTe) = 80.400 ± 0.027 (stat) ± 0.040 (syst) GeV mW(pTn) = 80.402 ± 0.023 (stat) ± 0.044 (syst) GeV

Summary of direct measurements20

Higgs Mass ConstraintsMH from Standard fit:• Central value ±1: • 2 interval: [42, 158] GeV

Green band due to Rfit treatment of theory errors, fixed errors lead to larger 2

min

MH from Complete fit:• Central value ±1: • 2 interval: [114, 153] GeV

MH 116 1.3 16 GeV

Complete fitStandard fit

MH 80 23 30 GeV

Andreas Hoecker (CERN)EPS 2009

22

The future…

D0 e only

23

Elastically scattered electrons

Quartz barcosmic tests

QWeak Parity violation in e-p scattering at Q2 = 0.026 (GeV/c)2.

Scheduled for ~223 days at 1.165 GeV. Start construction 2009End data taking 2012

24

Qweakincreasing

Qweakdecreasing

far close

scale dependence of weak mixing angle in MS schemeRunning of sin2qw

screening

anti-

scre

enin

g

PDG 2008 Review: “Electroweak and constraints on New Physics Model” J. Erler & P. Langacker

DIS08 - UCL

25

April 8, 200825

NuSonG neenee

Proposed 5 kT fine grained neutrino detector using a revived Tevatron neutrino beam

~1G DIS events measure r and sin2qw

Structure Functions 70K nee nee 7K anti-nee anti-nee

measure r and sin2qw

700K nme nem for clean flux measurements

11

2

22

21

1

26

Dibosons and Anomalous Couplings

Last year, CDF and D0 finished off the dibosons (except for HW)

6 ZZ llll events between the two experiments with minimal background

CDF 3m+t event

27

Summary of Bosons at the Tevatron

28

What to do for an encore? Highlights this year are

Use of much larger data samples the difficult channels with Z vv and W/Z

jj. Improved limits on anomalous couplings

29

General Effective Lagrangian for charged (WWγ/WWZ):

νλμν

*λμ2

W

Vμνν

*μV

μνν

*μ

νμ*μν

V1

WWV

WWV VWWMλi VWWiκ)WVWVW(Wigg

L

ρν*

μλνλ*

μμνλρV

5μννμ

ν*

μV4 V WWWWεgVVWWg- νλμ

ν*

λμ2W

Vμνν

*μV VWWM

λiVWWki ~~~~

General Effective Lagrangian for neutral (ZZγ/Zγγ):

EM gauge inv. (g1γ = 1), C and P conserving 5 couplings: κV, λV, g1

Z

νμα4

Z

2VαμνV

4μνV

2ν2Z

2V

μμνV

3μνV

1γZV VMm ZFhFhVM

m ZFhFhieL ~~ □□

CP conserving → h3,4V couplings (V = γ, Z)

: SM 0hλ 1,κg V3,4VV

Z1 :Deviations SM 0hΔh 0,λΔλ

1κΔκ 1,gΔgV3,4

V3,4VV

VVZ1

Z1

COUPLINGS ANOMALOUS

0 Δ

30

Charged Triple Gauge CouplingsProbed by WW, WZ, and Wγ productionGeneral Lagrangian has 14 parametersAssume EM gauge invariance and C and P conservation⇒ 5 TGC parameters: g1

Z, kγ, kZ, λγ, λZ

g1 and k are 1 in the SM, the rest are zero

Neutral Triple Gauge CouplingsProbed by ZZ and Zg productionGeneral Lagrangian has 8 TGC parametersAssume CP conservation⇒ 4 non-SM TGC parameters: h3

γ, h3Z, h4

γ, h4Z all

0 in SM

31

Strategies These are very rare processes First do pure leptonic final states

Very small statistics Very low background

New! 3-5 times more data analyzed New! Can use more difficult signatures to get more

statistics Z+g vvg is harder W+W/Z lvjj is really hard Z + W/Z vvjj is really really hard

Wg lngZg ll gWW lnlnWZ lvllZZ llll observation by D0 and CDF in 2008

32

nng candidate event

g

MET

Mike StrangThursdayEWK II

g

33

Zg vvgSelect interactions with large,

significant Missing transverse momentum

Zg vvg avoids radiation off of the Z!

Limits on the anomalous couplings of Z’s to photons. The standard model wants 0

34

CDF WW lvlv with 3.6 fb-1

Use matrix method likelihood method to assign probability to signal/background based on event kinematics

35

CDF Observation of VV MET+jj

18±2.8(stat)±2.4(syst)±1.1(lumi) pb 16.8±0.5 pb (SM)

Events with 2 jets and MET > 60 GeV and high MET significance

Eric JamesThursdayEWK III

arXiv:0905.4714

36

Charged Anomalous Couplings

Set limits on charged Anomalous couplings

37

D0 – set charged TGC limits using pt in 4 channels

WZ→lvll

Wγ→lvγ

WW lvjjWW→lvlv

JadrankaSekaricThursdayEWK III

38

D0 limits on anomalous couplingsfrom Wg, WW, WZ

Can be interpreted as measurements of the magnetic dipole and quadrupole moments.

39

Prospects for the future D0 and CDF can anticipate 3-10

times more data per channel Combining channels and

experiments will increase the TGC sensitivity by a factor of 3-5.

LHC experiments have 10 times the cross section 10 fb-1 of data factor of 100 in statistics and 10 in sensitivity relative to current Tevatron.

200 fully reconstructed ZZ events in first 10 fb-1 !!

ATLAS PROJECTIONS from MTWW

ZZ polarization 100 fb-1

( Eyal Brodet ATLAS)

40

Electroweak summary Major progress Precision EWK

W mass precision on track for 25 MeV/expt at Tevatron – maybe 10 MeV at LHC!

We are at the beginning of a new generation of measurements of sin2qW at colliders and fixed target

DiBosons All diboson channels seen even in hadronic final states LHC will have enough statistics to do precision

measurements of couplings and event kinematics very soon!

42

BACKUP slide

43

46

s

(nb

)

103

107

106

109

100

103

√s (TeV)1 10

0.01

108

105

102

101

104

106

p-p (or p-p)

Rate

s per

seco

nd a

t 103

2

WZ

b

jet>100

top

higgs?

total

WWWZZZ