bsm searches at hera
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BSM searches at HERA
John MartinUniversity of Toronto / ZEUS
for H1 and ZEUS
LISHEP 2006 J. Martin 2
Running conditions
HERA-II running very well Lumi high and still increasing
for both e+p and e-p (1.5 pb-
1/day achieved) Polarization at ~ 40% Expect >600 pb-1/expt. from
HERA-II by June 2007 (HERA-I was ~120 pb-1/expt.,
almost all e+p)
e-p 215 pb-1
2005
LISHEP 2006 J. Martin 3
Outline
General BSM searches Intriguing excess in isolated lepton events? Multi-lepton events
Search for eq type resonances HERA good for single particle production with
Yukawa coupling to eq LQ, Rp violating SUSY, LFV Gaugino and gravitino searches
Contact interactions Magnetic monopoles
NB: HERA generally has little SM background for BSM searches
Q2
e e,
p
xP
LISHEP 2006 J. Martin 4
General search
H1: model independent search for new phenomena by topology (as D0)
isolated, high PT particles: e, , , jet,
PTpart > 20 GeV, 10 < part < 140, D(- )part >
1.0
use probability estimator sensitive to narrow resonances, unusual events, broad signals similar sensitivity to dedicated searches
basic agreement with SM, except …
-j- : 4 data / 0.8 ± 0.2
Data from HERA-I
LISHEP 2006 J. Martin 5
Intriguing excess at H1…
Isolated leptons and missing PT
X
e, SM W production ~ 1 pb-1
Background from mis-measured DIS and di-lepton events
H1
e+p
e-p
LISHEP 2006 J. Martin 6
The latest H1 numbers
Choose cut at PTX >25 GeV, ~ best discrimination
between background and decay of a heavy particle, like top.
% of SM expectation from W production
3.4 excess
LISHEP 2006 J. Martin 7
But ZEUS…
H1 continues to see an excess in e+p (recall HERA I was almost all e+p), but not in e-p
ZEUS doesn’t confirm H1 and ZEUS expectations from SM agree for electron
analysis ZEUS muon analysis not yet finished
Still a puzzle, more data needed
Isolated e candidates 12 < PTX < 25 GeV PT
X > 25 GeV
ZEUS (prel.) HERA I 99-00 (66 pb-1) 1 / 1.04 ± 0.11 (57%) 1 / 0.92 ± 0.09 (79%)
ZEUS (prel.) HERA II 03-04 (40 pb-1) 0 / 0.46 ± 0.10 (64%) 0 / 0.58 ± 0.09 (76%)
ZEUS e+p data with similar cuts, purity:
LISHEP 2006 J. Martin 8
Isolated events with PT,miss
hadrons use 6 jet-shape variables
to suppress QCD background
For PTX> 25 GeV
ZEUS observes 2 events expect 0.12 0.02 Anomalous top, stop, another
heavy particle?? But, H1 sees no events
Both Hera-I data, await HERA-II results…
What about the channel?
LISHEP 2006 J. Martin 9
Anomalous FCNC couplings Search for single top production via
W decay to e, , or jets
high PTX ( > 40 GeV, ZEUS)
H1 cuts Mt > 140 GeV
SM background negligible:
No evidence found, set limits H1 excess needs tu ~ 0.2, still just about compatible with FCNC top production
Iso-lepton events: single top?
Wbtu *
fb1 Xbtep
LISHEP 2006 J. Martin 10
Or bosonic stop decay?
Consider model with :
For bosonic decay, slight excess only in jPT
miss channel
No excess in ej channel
Iso-lepton events therefore unlikely to arise from bosonic decay of stop
LISHEP 2006 J. Martin 11
Search for 2 leptons (PT1 , PT
2 > 10, 5 GeV) in sample of 209 pb-1 (45 pb-1 e-p, 164 pb-1 e+p) - interactions ~ 1pb-1
Overall agreement with SM:
But, for PT > 100 GeV : Nobs = 4 (3 ee, 1 e Nexp = 0.81 0.14
3 ee, 3 eee, 2 eevents withM12 > 100 GeV
Multi-lepton events (H1)
e+p
H1 excess,not in ZEUS
LISHEP 2006 J. Martin 12
H1 analysis extended to include 05 data no new 2e/3e event at high M12 one new eμμ event at Mμμ > 100 GeV one new eμμ event at Meμ > 100 GeV
for ΣPT > 100 GeV:
Nobs = 4 Nexp = 1.1 0.2
highest ΣPT events appear in e+p collisions
Multi-lepton events (update)
(275 pb-1)
LISHEP 2006 J. Martin 13
Doubly charged Higgs?
H++(--) occurs in BSM models extending the Higgs sector, such as L-R symmetric models
Search for high mass di-leptons with same charge as beam
Only 1 ee event found, no ee events anomalous multi-lepton events unlikely to be
doubly charged Higgs, so set limits LEP, Tevatron better except for off-diagonal
couplings
LISHEP 2006 J. Martin 14
Generic Leptoquarks Search for resonance in e-jets, e-
Likelihood analysis in Mej, cos*
e+
e
LQ
LQ
q
q
LQ
LQ
depend on Yukawa coupling,
LQe
q
e,
q
LQ
e+
e
q
q
LQ
e
q
q
e
Coupling limits for BRW LQs
7 scalars, 7 vectors
LISHEP 2006 J. Martin 15
Comparison to Tevatron
HERA complementary to Tevatron: Tevatron good for high BR
to eq. Background is severe for q decay of LQ
HERA can reach to low BR to eq for reasonable coupling
LISHEP 2006 J. Martin 16
LQ mediated LFV
Search for high PT After optimizing cuts:
ZEUS: 0 candidates (SM: 0.43±0.08 , 2.3±0.5 ) H1: 1 candidate (SM: 0.56±0.16)
Low mass: set limits with ,eg, eq = q , q
High mass: set bounds on eq lq / M2LQ(TeV-2)
e: low energy limits generally better e: ZEUS results generally better
eb b
eb s
Similar results from H1best non-ZEUS limit
ZEUS limit
LISHEP 2006 J. Martin 17
R-parity violating SUSY
At HERA probe:
Search in both l-jet and gauge decays (multi-jets and leptons)
No evidence found at ZEUS or H1
e+ d u Lj via ’1j1
e- u d Rk via ’11k
~
~
'
LISHEP 2006 J. Martin 18
Limits largely independent of MSSM parameters Improved limits from HERA up to 255 GeV for
Coupling limits in MSSM H1: unconstrained model with
sfermion masses free parameters, gluino mass ~ M3 at EW scale (common gaugino mass m1/2 at GUT scale)
ZEUS: stop search with 1st and 2nd generation squark masses set to 1 TeV
LISHEP 2006 J. Martin 19
in mSUGRA assume also a common scalar mass m0 at GUT scale (gives a 5 parameter SUSY model)
H1 HERA-I data: LEP limits better except for stop Tevatron limits weaker
due to large branching ratio to jets + missing ET
HERA-II will improve sensitivity to RPV stop
Limits in mSUGRA model
L3 (tan = 2)
D0 Run Ij=1,2
LISHEP 2006 J. Martin 20
Gaugino production
Production by RPV t-channel slepton exchange
Search in ejj channel with multi-variate discriminant against NC DIS background
No deviation from SM
ZEUS Prelim., LP05
HERA extends LEP limits in part of parameter space
LISHEP 2006 J. Martin 21
For small m: neutralino masses up ~ 120 GeV are excluded for ’ = 1.0 Complementary to Tevatron,
where production is by pairs or
If gravitino is the LSP
Gauge mediated symmetry breaking (GMSB) has N extra “messenger” fields of mass M to transmit the SB NLSP is neutralino or slepton
Search for high PT + missing ET (bkgrd: radiative CC)
1
~ 02
~1
~
D0 bound
D0 bound
LISHEP 2006 J. Martin 22
Excited fermions
Fermion substructure excited fermions
For f/=1/MF* , 95% upper limits: e* 250 GeV (H1) q* 205 GeV (ZEUS) * 135 (f=f’), 158 (f=-f’) GeV (ZEUS)
for *, e-p 100x more sensitive than e+p
await HERA-II e-p analysis
..22
1 ** chFB
YfgWgfFL LRFF
LISHEP 2006 J. Martin 23
Contact interaction
HERA-I form factor fit gives Rq < 0.85 . 10-18 m Can also set limits on eqeq contact interactions
e-
e+
sRLji
jiL
,,,
4
Pari
ty c
onse
rvin
gu q
uark
only
APV
lim
its
Similar limits from LEP, Tevatron
n extra dimensions? Graviton exchange effective coupling
nD
nP MRM 22 ~
1,4
DSS
G MMM
Limits close to 1 TeV
LISHEP 2006 J. Martin 24
Magnetic monopoles?
Dirac monopoles: large magnetic charge, highly ionizing Some BSM models predict light monopoles Could stop in beampipe and stay trapped
Cut 1994-7 beampipe into strips passed through superconducting coil system sensitive to 0.1gD
4/2Dg gecgD 2/
LISHEP 2006 J. Martin 25
Summary
Many BSM scenarios have been studied at HERA Most results still from HERA-I (~120 pb-1/expt, almost all e+p) Competitive and/or complementary to LEP, Tevatron
Only possible sign of BSM physics are the anomalous W-like events from H1: need more data
HERA-II will provide a data set of > 600 pb-1/expt with lepton polarization, both e+p and e-p new sensitivity to BSM physics with higher cross section in e-p Still some chance of a discovery before the LHC
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