Electroweak Physics Searches

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Electroweak Physics Searches
Andrew Mehta
DIS 2003, St. Petersburg, 23-27 April 2003
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Contents

• New Electroweak results
• Search for SM Higgs
• Search for MSSM Higgs
• R Parity violating SUSY searches
• 2?ETMISS from Tevatron
• W? from Tevatron
• Leptons ETMISS from HERA
• Search for single top from HERA
• Leptoquarks
• Large extra dimensions
• Dijets from Tevatron
• Dileptons from Tevatron
• Search for magnetic monopoles

Only a small personal selection of many many
results - only collider experiments. Details in
parallel sessions.
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Status of Experiments
LEP (ee? pp ?slt209 GeV) - Final run Dec. 2000.
Many final data published eg. Higgs search.
HERA (ep ?s319 GeV) Run I (120 pb-1 per
experiment) completed. Many final Run I results
presented. Run II start up slow. High luminosity
and polarisation demonstrated. Awaiting
luminosity in summer 2003
Tevatron (pp ?s196 GeV) - Run II underway after
slow start. About 100 pb-1 per experiment so far
(same as Run I). Many new results. Most not yet
competitative with Run I, but soon will overtake
them
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Tevatron RunII EW Results
W?e?
Z?ee-
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W Mass Measurements
D I R E C T
I N D I R E C T
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New Mtop Measurements
179 3.6 6 GeV (D0 Run I Preliminary)
171.213.4 9.9 GeV (CDF Run II Preliminary)
Old Value 174.3 5.1 GeV (CDFD0 Published)
New more accurate D0 Run I result
First results from Run II more data needed
better calibrations
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Impact of Tevatron RunII
Can constrain Higgs Mass from Tevatron alone.
Expected Run II
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World Electroweak Results
Maximum deviation 2.94 sigma!
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Higgs Limits from EW Data
MH lt211 GeV (95 CL) (Does not include latest
top mass measurements)
Result not affected much by NuTeV deviation
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Direct Higgs Searches at LEP
Data now final (cern-ep-2003-011)
No large deviations of data seen in mass Spectrum
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Direct Higgs Searches at LEP
Excess around 99 GeV not relevant for SM
Higgs (MSSM though?).
No significant excess at 115 GeV in final LEP
data
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Direct Higgs Searches at LEP
No Higgs seen at LEP
MH lt114.4 GeV (95 CL)
Tevatron II EXPECTED search potential MH ?110
GeV (2 fb-1) MH ? 130 GeV (6.5 fb-1)
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Higgs Sector of MSSM

• Two Higgs doublets. CP conserved
• Physical Higgs bosons h and H (CP even), A (CP
  odd), H?
• Processes at LEP

Search rather similar to Standard Model Higgs
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MSSM Higgs Search
2? excess at mh?97 GeV
No strong evidence. Limits mA, mhgt?90
GeV (depends on model)
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Rp violating MSSM from HERA

• R parity 1 for known particles -1 for
  supersymmetric partners
• Rp violation ? SUSY particles can be singly
  produced LSP
• not stable

LQ like
Cascade decays
No excesses seen in any channel ? set limits.
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Rp violating MSSM from HERA
Unconstrained MSSM - free variation of ?, M2, tan
?
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Search for 2?ET Miss Tevatron
Remember CDF event?
DØ Run II Preliminary
Search in RunII data CDFD0 No events at large
ET Miss No event with an additonal lepton
(yet!)
Cross section limit lt0.9 pb
ET Miss
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2e2?ET Miss Event from Run I
Event still unexplained by SM processes
(10-6 events expected)
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Search for Wphoton
Run I Etgt25 GeV, lepton Etgt25 GeV, photon Etgt25
GeV
lepton Data SM exp
muon 11 4.2
electron 5 3.4
both 16 7.6
Excess seen in CDF Run I data
Excess not seen in Run II
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Leptons PT Miss from HERA
Look for isolated lepton missing PT
Only significant SM process is W production
X
Lepton
Example event
PT Miss
NLO SM W calculations now available Deiner et al.
(hep-ph/0203269)
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Leptons PT Miss at HERA
H1 e?, 94-00 e data, published
Data SM prob PTX lt
25 GeV 8 9.5 - PTX gt 25 GeV 10
3.0 0.0015
No taus yet

ZEUS e??, 94-00 e? data

Data SM prob e?, published PTX gt 25 GeV
7 5.7 0.34 ?, preliminary PTX gt 25
GeV 2 0.12 0.0068
Excesses seen at large PTX - region most likely
for new physics
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Leptons PT Miss at HERA
Discussion

• H1 sees excess in electron and muon channel
• H1 excess first seen in 94-97 data
• H1 excess also seen in 99-00 data
• ZEUS see no excess in electron or muon channels
• ZEUS see an excess in tau channel
• All together 19 data events SM 8.8 ( prob. 0.44
  assuming systematic error 15 )

? Not enough statistics for firm conclusion, need
more data
Q. Why does the SM expectation vary so much? A1.
Main reason for H1/ZEUS difference is a larger
non-W component in ZEUS data. A2. Tau channel has
much lower efficiency due to harsh cuts to
suppress CC background
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(Aside) Top from Tevatron
Top search results in very similar final state to
HERA events.
Any excess found in top analysis may be due
to same process
Jet
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Search for single top at HERA
t
t
Jet

• Anomalous single top production could explain
  leptonPTMiss
• Search possible in hadronic channel also
• SM rate negligible due to FCNC vertex tu?

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Anomalous tu? Coupling
HERA-assume iso. lep. events are SM fluctuations
and set limits on anomalous coupling
LEPTevatron sensitive too ? complementary
results from all 3 experiments
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Leptoquarks
HERA
Tevatron

• Quarks and Leptons have many symmetries (3?2)
  proton and electron charges equal
• Is there a higher symmetry? Leptoquarks with
  B?0, L?0
• LQs appear in many GUTs
• Buchmüller-Rückl-Wyler model predicts 14 LQs
• (7 scalar, 7 vector) - F0 for eq, F2 for
  e-q
• Yukawa coupling ?.
• BR fixed ?eq1, 0.5 , ??q 0, 0.5

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Leptoquarks
Data from HERA
No excess seen ? place limits
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Leptoquarks
Tevatron run II data give similar limits to run I
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Rutherford scattering off a Quark
At very high 4 momentum transfer DIS at HERA
probes distances 1/1000 th size of proton If
the quarks had substructure the DIS cross section
would be modified
Quarks have radius lt0.7 ?10-16 cm
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Large Extra Dimensions in DIS

• Arkani-Hamed, Dimopolos Dvali sugggest
  gravitons propagate
• in 4n dimensions (PLB 544 (1988) 263).
• Extra dimensions curled up within size R, Mpl2
  Rn Msn2
• Ms is thought to be of order mew
• ? n1 R solar system
• n2 R 1 mm

In DIS virtual graviton exchange effects
eq?eq No deviations found Limits of Ms gt0.8 TeV
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Large Extra Dimensions at LEP
Similar effect at LEP (Interference with t
channel ee ?ee)
Combined LEP limit Msgt1 TeV
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DiJets from Tevatron
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DiJets from Tevatron

• Many models produce
• such particles
• Masses up to 840 GeV
• ruled out

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DiLeptons from Tevatron
Good description by SM
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DiLeptons from Tevatron
Limits for Sequential Standard Model Z'
Same data used for other constraints eg. Graviton
mass in LED model
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Search for Magnetic Monopoles
Monopoles should be stopped in beam pipe
and remain
Method cut beam pipe into strips and pass through
solenoidal field
Current induced in solenoid measured in SQUID
magnetometer
Mimic monopole by attaching a solenoid to one end
of strip
Dipoles currents return to original
value Monopole signal shows a current increase
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Search for Monopoles
No monopoles seen ?set limits
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Conclusions

• Nearly final electroweak results from LEP now
  available. Still no explanation of 2.94 deviation
  by NuTeV.
• New techniques being developed at Tevatron to
  reduce error on top W masses
• LEP definitely did not see Higgs
• Tevatron run II well underway - many first
  search results
• Looking forward to HERA run II data
• No evidence for physics beyond the standard
  model. Some interesting hints though - run II
  data HERATevatron needed