EW
at
HERA
and “RELATED” NEW PHYSICS
Luca Stanco – INFN Padova
on behalf of ZEUS and H1 collaborations
Luca Stanco - Padova
- HERA: a QCD and EW
machine
Results on:
- EW constraints
- Isolated Leptons
- Single TOP
EW and NP at HERA, Photon 2009
1
HERA: a collider e-p
ZEUS
H1
1993-2007
Last Fill the 30th June 2007
0.5 fb-1 per exp.: e+p, e-p, LowEnergyRange, MER
Luca Stanco - Padova
EW and NP at HERA, Photon 2009
2
HERA: the QCD machine
For Q2 ≈ M2Z,M2W study also EW interactions:
CC double diff.
cross-section
Beam Polarization
Luca Stanco - Padova
QPM Structure Functions
EW and NP at HERA, Photon 2009
3
HERA-II feature: Polarization
Luca Stanco - Padova
EW and NP at HERA, Photon 2009
4
Q2 ∼ 1/l : the scale of the interaction
corresponds to the spatial resolution
at which the proton structure is probed
Luca Stanco - Padova
EW and NP at HERA, Photon 2009
5
ElectroWeak unification: status-of-the-art
Neutral
Current
e-p (ZEUS publ., H1 prel.)
e+p (ZEUS prel., H1 prel.)
Charged
Current
e-p (ZEUS publ., H1 prel.)
e+p (ZEUS prel., H1 prel.)
M2Z and M2W
dominate
exhanges
( corrected for the
Polarization effects )
Luca Stanco - Padova
EW and NP at HERA, Photon 2009
6
NC and Structure Functions: Parity Violation test
Luca Stanco - Padova
EW and NP at HERA, Photon 2009
7
Weak Interaction check with Polarization (CC)
V-A chiral structure
(ZEUS preliminary 2007)
WR>208 GeV
Luca Stanco - Padova
EW and NP at HERA, Photon 2009
8
Weak Interaction check with
Polarization (NC)
Asymmetry proportional
to vector coupling
Parity Violation size,
demonstrated down to 10-18 m
Luca Stanco - Padova
EW and NP at HERA, Photon 2009
9
DGLAP fits for QCD-EW: PDFs’ and uv-quarks couplings
- Simultaneous test of the EW and Strong sectors of SM
- Best determination of u-coupling to Z
- Competitive with Tevatron and LEP results
Luca Stanco - Padova
EW and NP at HERA, Photon 2009
10
Isolated high-pT leptons: status-of-the-art
Final analysis from H1 and ZEUS on Electron and Muon leptons
H1 looked also at the Tau leptons: challenging, large background
(combined in progress)
nice Jacobian peaks,
however at hight pT…
Luca Stanco - Padova
EW and NP at HERA, Photon 2009
11
Gerard Brandt at DIS09
H1:
Luca Stanco - Padova
EW and NP at HERA, Photon 2009
12
Anomalous Single TOP production at HERA
Final results from H1 (HERAII: 474 pb-1), HERAI+II in DESY-09-50
ZEUS preliminary: 277 pb-1 (HERAII), combined with HERAI (120 pb-1)
Neglet c and Z couplings.
Sensitive to u (valence) and anomalous g exchange
Search for signal in muon, electron, hadron channels
Intrinsic background from SM production of W (lepton decay)
Luca Stanco - Padova
EW and NP at HERA, Photon 2009
13
No excess  limits, H1: s < 0.25 pb, ktug < 0.18, ZEUS: s < 0.13, ktug < 0.13
(slight excess)
Stefano Antonelli at DIS09
Luca Stanco - Padova
EW and NP at HERA, Photon 2009
14
Conclusions
• H1 and ZEUS exploit most of HERA DATA
for EW studies
• Unique HERA results done and undergoing
• Many EW checks,Universality, Chiral Structure,
Parity Violation
• Single W production, measured,
intriguing signal left at hight pT
• Anomalous Single TOP production,
SM checked (Colliders complementarity)
BIG thanks to HERA !!
Luca Stanco - Padova
EW and NP at HERA, Photon 2009
15
Backup Slides
Luca Stanco - Padova
EW and NP at HERA, Photon 2009
16
Chiral Structure of CC, by ZEUS
DESY-08-177
Total cross-section
vs Electron Polarization
provides striking evidence
Luca Stanco - Padova
EW and NP at HERA, Photon 2009
17
Isolated Lepton yield
Luca Stanco - Padova
EW and NP at HERA, Photon 2009
18
Single TOP production at HERA in the SM
Luca Stanco - Padova
EW and NP at HERA, Photon 2009
19
Single TOP results from H1
Slight excess in the muon
and electron channels
Luca Stanco - Padova
EW and NP at HERA, Photon 2009
20
Single TOP results from ZEUS
Muon channel
Luca Stanco - Padova
EW and NP at HERA, Photon 2009
21