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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.

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Searches and ew physics at hera l.jpg

Searches andEW physics at HERA

5th Rencontres du VietNam 2004

New Views in Particle Physics

Sascha Caron (NIKHEF)

(former Aachen)

HERA

P(920 GeV)

e(27.5 GeV)


Slide2 l.jpg
HERA

HERMES

HERA collides 27.5 GeV e±

with 920 GeV protons at

√s=320 (300) GeV

HERA-B

HERA2 – luminosity, polarized

e beam and detector upgrades

Lumi produced by HERA (pb-1)

  • 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)

day of running

Sascha Caron (NIKHEF) at Recontres du Vietnam 2004


Hera physics on 1 transparency l.jpg
HERA physics on 1 transparency

NC deep inelastic scattering

CC deep inelastic scattering

Q2 = - squared momentum transfer between e and p

W production

Multilepton production

Sascha Caron (NIKHEF) at Recontres du Vietnam 2004


Searches and ew physics at hera4 l.jpg

Electroweak tests in deep inelastic scattering

Systematic tests of the SM at high PT

Measurements of W production and multi-lepton processes

Various dedicated searches for new physics:

SUSY, Contact Interactions, Quark Radius, anomalous

top couplings, LQ, H++, magnetic monopoles, large ED, excited fermionsand more

Searches and EW physics at HERA

Sascha Caron (NIKHEF) at Recontres du Vietnam 2004


Deep inelastic scattering at hera l.jpg
(Deep) inelastic scattering at HERA

HERA probes eqinteractions

at photon virtualities Q2

from ≈ 0 (photoproduction, γq)

up to 4*104 GeV2

NC

unique facility

CC

Test of EW sector with

W (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 2004


Contact interactions l.jpg

Results on: Leptoquarks,

general Contact Interactions,

Large Extra Dimensions,

Quarks Radius

Contact Interactions

New interactions between

e and q can be modeled by

4-fermion contact interactions

Parametrized by additional

terms in the lagrangian

Limits on quark radius

(classical form factor):

Rq< 10-18 m (ZEUS and H1)

or vector contact interaction

couplings of up to 5 TeV

Sascha Caron (NIKHEF) at Recontres du Vietnam 2004


Slide7 l.jpg

A general Search for

new 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 2004


Slide8 l.jpg

A general search

for new phenomena

Mall and ΣPT

distributions

are systematically

investigated using

a search algorithm:

Find in each channel

the region with the

greatest deviation

Sascha Caron (NIKHEF) at Recontres du Vietnam 2004


Slide9 l.jpg

A general search for

new phenomena

Derive for each event class

the probability P to observe

a deviation anywhere in the

spectrum as large as found in

the data

^

^

Smallest P found in

μ-jet-ν, e-jet and e-e

channels

Repeat the whole analysis

with many MC (pseudo data) experiments each with the H1 luminosity

About 3% (Σ PT) and 25% (Mall) of

MC experiments have a deviation

larger than that of μ-j-ν final state

Sascha Caron (NIKHEF) at Recontres du Vietnam 2004


Isolated lepton events l.jpg
Isolated lepton events

ep → jet (PT,X)+ PT,miss+ lepton

main SM contribution is W production

Results from dedicated analysis:

HERA 1:

e

p

(observed/expected)

Agreement in hadronic channel

(with large background)

HERA 2:

excess of events at H1

no excess in HERA1 ZEUS data

clarification needs more lumi

Sascha Caron (NIKHEF) at Recontres du Vietnam 2004


Anomalous top production l.jpg
Anomalous top production

Compare the l-jet-ν events

with models, e.g. single top

production with anomalous

couplings between tuZ and

tuγ

Selection cuts optimized for

top

H1: excess in leptonic channels

(3e, 2μ with SM exp. 1.3 ± 0.2)

no excess in hadronic channel

ZEUS: no excess in hadron or

lepton channels

Limits on top cross sections and couplings

Sascha Caron (NIKHEF) at Recontres du Vietnam 2004


Multilepton events l.jpg
Multilepton events

Measurement of multilepton events

Process: 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 2004


Susy@hera l.jpg
[email protected]

Example: sbottom production

HERA: RP violating SUSY

→ single production of squarks

via couplings Λ’ijk

Large variety of squark decay modes

→ many final states are considered

For λ’=0.3 : Msquark>275 GeV for

all squarks types in nearly full parameter space

small couplings: improvement of

indirect low-energy limits

Also interpretations in terms of MSUGRA model parameters

Sascha Caron (NIKHEF) at Recontres du Vietnam 2004


Summary l.jpg
Summary

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 !

Sascha Caron (NIKHEF) at Recontres du Vietnam 2004


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