hep2008-olympiath. d. papadopoulou1 neda, the unique river with a feminine name ! theodora d....
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HEP2008-Olympia Th. D. Papadopoulou1
Neda, the unique river with
a feminine name !
Theodora D. Papadopoulou
( coming from the highland of Olympia…)
NTU Athens
H1 Collaboration
Hellenic HEP2008 - Olympia - April 17, 2008
HEP2008-Olympia Th. D. Papadopoulou2
H1, Z.Phys. C74 (1997)191
ZEUS, Z.Phys. C74(1997)207
Do we have surprises from HERA nowadays ?
HEP2008-Olympia Th. D. Papadopoulou3
Outline
HERA I + HERA II
CC and NC Cross section measurements
Quark form factor
Contact Interactions
Leptoquarks & LFV
Search for SUSY quarks
Isolated Leptons with P(Τ)-missing
Multi-lepton search
HERA to LHC physics
Outlook - As an Epilogue
HEP2008-Olympia Th. D. Papadopoulou4
HERA II: ep collisions with e-/e+ polarisation
• Detector and Luminosity upgrade
• large backgrounds identified and
overcome in 2002/ 03
• efficient data taking since 10/ 03
• HERA operated until 1 July 2007
• polarized e-/e+ beam with spin rotators
HEP2008-Olympia Th. D. Papadopoulou5
HERA I / HERA II
• World’s unique e p Accelerator
and Collider
• Operated 1992 -2007
• H1 & ZEUS each have collected
0.5 fb ¹־ of high quality Physics
data balanced in e±
• 72 % of the Luminosity is from
HERA II longitudinally polarized
e± beams
• Polarization typically 30 – 40 %
HEP2008-Olympia Th. D. Papadopoulou6
Searches for new currents affecting the DIS process
Deep Inelastic Scattering precision experiments• Measure E’e , θe , Eh , θh
[ 0.3 –1% ; 0.2-1mrad; 1-2%, 1-2mrad ]
reconstruct x , Q2 : kinematics is
overconstrained• Highly Efficient 4π Detectors (Calorimeters, Chambers in solenoid field)• Accurate run vertex (upgrade)
(drift chambers: 200 μm and
Si trackers: 20 μm resolution )
• Luminosity from Bethe-Heitler scattering
[ ep epγ ] theoretical error ~ 0.5 %
HERA I lum. error was 1.5 %
HERA II lum error in average was 3.5 %
HERA II
HEP2008-Olympia Th. D. Papadopoulou7
Cross section measurements with HERA
DIS is the golden process to study the structure of matter
(and at HERA the structure of proton)
Measurements up to ~ 40000 Q2
Electroweak Unification
N C
C C
HEP2008-Olympia Th. D. Papadopoulou8
Quark radius limit
Quarks are pointlike down to
proton radius/1000
H1 : < 0.74 10-18 m
ZEUS: < 0. 67 10-18 m
qR
qR
HEP2008-Olympia Th. D. Papadopoulou9
CC polarised cross sections (HERA II)
Total CC cross section (Q2 > 400 GeV, y < 0.9 ) vs. polarisation
H1 and ZEUS measurements consistent with SM
no right handed CC limit on right-handed W : M(WR ) > 208 GeV
CDF limit : M(WR ) > 790 GeV
Extrapolation to P = ± 1 in SM
σ (RH) =0 for electrons and σ (LH) =0 for positrons and the total cross-section changes linearly with polarisation.
nonexistence of RH currents within the framework of SM.
HEP2008-Olympia Th. D. Papadopoulou10
Contact Interactions
•Parametrisation of new physics
due to composite fermions or
New heavy mediators ( mX >> )
Λ is the energy scale of new physics
s
Limits on ε Λ:
Similar sensitivity achieved at Tevatron
Limits set by looking for deviations from SM
limits Λ+ , Λ- , correspond to constructive, destructive interference with SM
(g2 = 4π ,
ZEUS
ZEUS: Λ > 2.0 – 8.0 TeV
H1 : Λ > 1.6 – 5.5 TeV
at 95% CL
1994- 2006 data
HEP2008-Olympia Th. D. Papadopoulou12
Leptoquarks at HERA
ep is the golden machine to study LQs
SEARCH FOR 1rst GENERATION LQs
BRW Model
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LQ existing Bounds
From EPS-2003 , A. Zarnecki
.)1(2/1 genS rstL
SCALAR LQs WITH F=0
H1 (94-00) e+pH1 Coll. Phys. Lett B629(2005)9
for λ ~ 0.3 mass exclusion ~ 275 – 325GeV depending on LQ type Similar limits obtained by ZEUS
HERA limits beyond LEP & Tevatron
HEP2008-Olympia Th. D. Papadopoulou15
LQ data analysis HERA I + HERA II
Data consistent with SM
All H1 / HERA I + II e+ p and e- p data
from I. Panagoulias’ talk at DIS2008 – work on PhD / NTUA
NCCC
HEP2008-Olympia Th. D. Papadopoulou16
LQ Exclusion Limits -- comparison with LEP and Tevatron
HERA extends the exclusion region
from I. Panagoulias’ talk at DIS2008 – work on PhD / NTUA
HEP2008-Olympia Th. D. Papadopoulou17
Search for Lepton Flavor Violation
Limits on Yukawa Coupling
assuming λeq = λ μq
I. Panagoulias, NTUA DIS08
e p μ Χ
2 events seen/ 2.2 ± 0.6 expected
HEP2008-Olympia Th. D. Papadopoulou18
R-parity Violation
• What is Rp and why go beyond ?
a discrete multiplicative symmetry in SUSY models connected to matter parity
R p = 1 for SM particles
R p = -1 for SUSY particles
o SUSY particles produced in pairs
o LSP is stable
o experimental signature of SUSY E T miss
fast proton decay is suppressed
HEP2008-Olympia Th. D. Papadopoulou19
RpV Superpotential
kjikjikjikjikjikji DDUDQLELL W
• Rp can be explicitly broken by trilinear terms in the superpotential
o single sparticle production via a ΔL 0 or a ΔB 0 operator
o Unstable LSP !
fast proton decay is suppressed if Lepton and Baryon number Violating Couplings not simultaneously present
0L 0L 0B
9 Couplings )( ji 27 Couplings 9 Couplings )( kj
HERA
• Resonant squark production at HERA
• l +( l ) + multijets
HEP2008-Olympia Th. D. Papadopoulou20
Beyond minimal LQs: SUSY quarks
H1 data : 64.3 pb-1 , 13.5 pb-1 e-p
H1 Coll. EPJ C36 (2004) 495 :
• all squark types
• all decay modes
For λ’ = 0.3 ( λ’ 2/ 4π = αem )
squarks can be ruled out
up to ~ 270 – 280 GeV
Constraints within the MSSM
HEP2008-Olympia Th. D. Papadopoulou22
Isolated leptons : Results 1994-2005
H1 e+p data H1 e-p data • H1 excess only appears in e+p data
• Fluctuations?(3.4σ)
New Physics?
• No new events on 2005 e-p events with ΣΕΤ>100 GeV
• The excess had to be clarified with the full HERA II data sets
HEP2008-Olympia Th. D. Papadopoulou23
Isolated leptons : Results HERA I + II
H1 e+p data H1 e-p data
All H1 / HERA I + II data : 478 pb-1
• Events at high PTX also observed in latest data
• Different observations in e+p and e-p data
• ZEUS : Agreement with SM expectations
XTP
σ ~ 1.3 pb
• but expect
small PTX
SM W e, μ
production
HEP2008-Olympia Th. D. Papadopoulou24
Isolated leptons : H1 and ZEUS Combined Results
• H1 and ZEUS combined in a common phase space
Total luminosity : 0 . 97 fb-1
• Good agreement with the SM
• Fluctuation in e+p for PTX > 25 GeV is reduced to 1.8 σ
XTP
HEP2008-Olympia Th. D. Papadopoulou25
Multi-lepton Events ( e, μ )
• All H1/ HERA I + II data with total luminosity : 459 pb-1
• look for events with at least 2 isolated high PT leptons (e, μ)
Topologies : ee, eμ , μμ , eee, eμμ
• Interesting events observed for ΣpΤ > 100 GeV
• H1 in e+p : Data/MC = 4 / 1.2 ± 0.2 events
• ZEUS : good Data/MC agreement with multi-electrons
Low SM background mainly produced
via γγ scattering
BUT waiting for
ZEUS multi-muons
VERY narrow possible surprise ?
HEP2008-Olympia Th. D. Papadopoulou26
Multi-lepton events : H1 and ZEUS Combined Results
• H1 and ZEUS combined in a common phase space
Total luminosity : 0 . 94 fb-1
• Few high PΤ events observed mainly in e+ p
for luminosity 0.56 fb-1 : Data/SM = 5 / 1.82 ±0.21 events
HEP2008-Olympia Th. D. Papadopoulou27
HERA to LHC
• low x physics at HERA : PDFs forward at LHC
• medium x physics at HERA plateau region at LHC
HEP2008-Olympia Th. D. Papadopoulou28
Kinematic Range
Dominant Contribution
Contributes when Q2 ~ M2Z
Contributes only at high y
HERA PDFs extrapolate into the LHC region and their accurate determination are crucial to New Physics measurements at the LHC such as compactified extra dimensions and contact int.
HEP2008-Olympia Th. D. Papadopoulou29
Triumph of pQCD !
The accurate measurements of HERA II especially on the F2 , FL
structure functions, the low-x PDFs and the high-x gluon PDF are VERY important for the LHC DISCOVERY POTENTIAL !
New HERA-I PDF fit predictions vs H1/ZEUS combined data for NC e+p on PDF fit
HEP2008-Olympia Th. D. Papadopoulou30
Direct Measurement of FL
x – averaged FL as a function of Q2 : consistent with QCD prediction
FIRST
PRELIMINARY
HEP2008-Olympia Th. D. Papadopoulou31
HERA to LHC
“Physics with HERA will be of much use when the physics at LHC becomes real.”
Max Klein
Hadron Collider Physics Conference July 2005
HEP2008-Olympia Th. D. Papadopoulou32
Outlook• HERA II run ended on July 1, 2007 with L ~ 1 fb-1
for both experiments H1 and ZEUS
• Combined analyses are underway towards the
final results
• Results from HERA experiments are consistent
and in good agreement with each other :
It is a triumph of pQCD !
• No evidence for New Physics at HERA
( No significant excess)
• Important contribution of HERA results
to LHC physics
HEP2008-Olympia Th. D. Papadopoulou35
Polarised Cross-sections
After the upgrade, HERA provides the experiments with longitudinally polarised lepton beams
The transverse polarisation builds up naturally (Sokolov-Termov effect)
Spin rotators flip the polarisation by 90º just before the lepton beam enters the interaction regions of experiments
Typical level of polarisation is ~ 40 %
Polarisation :
In SM σ (RH) =0 for electrons and σ (LH) =0 for positrons and the total cross-section changes linearly with polarisation.
nonexistence of RH currents within the framework of SM.
HEP2008-Olympia Th. D. Papadopoulou36
D* p resonance in 3 GeV region- Pentaquark
Katja Kruge talk – DIS08
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