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Searches and EW physics at HERA. 5 th Rencontres du VietNam 2004 New Views in Particle Physics. Sascha Caron (NIKHEF). (former Aachen). HERA. P(920 GeV). e(27.5 GeV). HERA. HERMES. HERA collides 27.5 GeV e ± with 920 GeV protons at √s=320 (300) GeV. HERA-B. - PowerPoint PPT Presentation
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Searches andSearches and EW EW physics at HERAphysics at HERA
55thth Rencontres du VietNam 2004 Rencontres du VietNam 2004New Views in Particle PhysicsNew Views in Particle Physics Sascha Caron (NIKHEF) (former Aachen)
P(920 GeV) e(27.5 GeV)
HERA
Sascha Caron (NIKHEF) at Recontres du Vietnam 20042
HERAHERA
Recorded data samples: HERA 1:•≈40pb-1 e+p (300 GeV)•≈15pb-1 e-p (320 GeV)•≈65pb-1 e+p (320)HERA 2:•≈50pb-1 e+p (320)
HERA collides 27.5 GeV e±
with 920 GeV protons at √s=320 (300) GeV
Lum
i pro
duce
d by
HE
RA
(pb
-
1)
day of running
HERMES
HERA-BHERA2 – luminosity, polarizede beam and detector upgrades
Sascha Caron (NIKHEF) at Recontres du Vietnam 20043
HERA physics on 1 transparencyHERA physics on 1 transparency
Q2 = - squared momentum transfer between e and p
NC deep inelastic scattering CC deep inelastic scattering
W production Multilepton production
Sascha Caron (NIKHEF) at Recontres du Vietnam 20044
Searches and EW physics at Searches and EW physics at HERAHERA
o Electroweak tests in deep inelastic scattering
o Systematic tests of the SM at high PT
o Measurements of W production and multi-lepton processes
o Various dedicated searches for new physics: SUSY, Contact Interactions, Quark Radius, anomalous
top couplings, LQ, H++, magnetic monopoles, large ED, excited fermions and more
Sascha Caron (NIKHEF) at Recontres du Vietnam 20045
(Deep) inelastic scattering at HERA(Deep) inelastic scattering at HERA
NC
CC
HERA probes eq interactionsat photon virtualities Q2
from ≈ 0 (photoproduction, γq)up to 4*104 GeV2
unique facility
Test of EW sector withW (CC) and gamma/Z (NC)propagators
Unification of weak and e.m.forces at high Q2
(more in HERA QCD talks)
Sascha Caron (NIKHEF) at Recontres du Vietnam 20046
Contact Interactions Contact Interactions
Limits on quark radius(classical form factor):Rq< 10-18 m (ZEUS and H1)or vector contact interaction couplings of up to 5 TeV
Results on: Leptoquarks,general Contact Interactions,Large Extra Dimensions,Quarks RadiusNew interactions between
e and q can be modeled by 4-fermion contact interactionsParametrized by additional terms in the lagrangian
Sascha Caron (NIKHEF) at Recontres du Vietnam 20047
A general Search for A general Search for new phenomenanew phenomena• Systematic search for deviations from the SM• All final states are considered in one analysis• Objects (e, μ, jet, γ, ν) with PT>20 GeV are analyzed • Data is classified to exclusive channels • Good agreement for (almost) all channels
Event yields are also available for HERA2 data!
Sascha Caron (NIKHEF) at Recontres du Vietnam 20048
A general searchA general searchfor new phenomenafor new phenomena
Mall and ΣPT
distributions are systematically investigated using a search algorithm:
Find in each channelthe region with thegreatest deviation
Sascha Caron (NIKHEF) at Recontres du Vietnam 20049
A general search for A general search for new phenomenanew phenomena
Derive for each event class the probability P to observea deviation anywhere in the spectrum as large as found inthe data
Repeat the whole analysis with many MC (pseudo data) experiments each with the H1 luminosity
Smallest P found inμ-jet-ν, e-jet and e-e channels
About 3% (Σ PT) and 25% (Mall) ofMC experiments have a deviationlarger than that of μ-j-ν final state
^
^
Sascha Caron (NIKHEF) at Recontres du Vietnam 200410
Isolated lepton eventsIsolated lepton events
PTx>25GeV e channel μ Τ
H1 e+p
(118 pb-1)
4/1.48±0.25 6/1.44±0.25 0/0.53
ZEUS
(130 pb-1)
2/2.9±0.5 5/2.75±0.2 2/0.12
e p
ep → jet (PT,X)+ PT,miss+ lepton
Results from dedicated analysis:HERA 1:
PTx>25 GeV e channel μ
H1 e+p
(45 pb-1)
3/0.74±0.15 0/0.76±0.1
HERA 2:
main SM contribution is W production
Agreement in hadronic channel(with large background)
excess of events at H1 no excess in HERA1 ZEUS data clarification needs more lumi
(observed/expected)
Sascha Caron (NIKHEF) at Recontres du Vietnam 200411
Anomalous top productionAnomalous top production
Compare the l-jet-ν events with models, e.g. single topproduction with anomalous couplings between tuZ andtuγ
Selection cuts optimized fortop
H1: excess in leptonic channels (3e, 2μ with SM exp. 1.3 ± 0.2) no excess in hadronic channelZEUS: no excess in hadron or lepton channels
Limits on top cross sections and couplings
Sascha Caron (NIKHEF) at Recontres du Vietnam 200412
Multilepton eventsMultilepton events
Mll>100 GeV ee channel eee channel
H1 HERA1+2
(165 pb-1)
3/0.44±0.1 3/0.31±0.08
ZEUS
(130 pb-1)
2/0.77±0.1 0/0.37±0.04
Measurement of multilepton eventsProcess: ep → ll (e) mainly via 2-photon collisions
Some interesting events at high mass:
No excess in muon channels
Sascha Caron (NIKHEF) at Recontres du Vietnam 200413
SUSY@HERASUSY@HERAHERA: RP violating SUSY→ single production of squarksvia couplings Λ’ijk
Also interpretations in terms of MSUGRA model parameters
For λ’=0.3 : Msquark>275 GeV forall squarks types in nearly full parameter space
small couplings: improvement of indirect low-energy limits
Large variety of squark decay modes→ many final states are considered
Example: sbottom production
Sascha Caron (NIKHEF) at Recontres du Vietnam 200414
SummarySummary
High energy ep collisions at HERA are a unique testing ground for the SM
Various searches for new physics are performed (model independent and dedicated)
Some interesting events are found
… and HERA 2 has just started !