hep2008-olympiath. d. papadopoulou1 neda, the unique river with a feminine name ! theodora d....

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


H1, Z.Phys. C74 (1997)191

ZEUS, Z.Phys. C74(1997)207

Do we have surprises from HERA nowadays ?


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


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


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 %


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


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


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


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.


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


Leptoquarks

b e ( μ )

LQ

s μ ( e )


Leptoquarks at HERA

ep is the golden machine to study LQs

SEARCH FOR 1rst GENERATION LQs

BRW Model


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


LQ data analysis

H1 (94 - 00) data


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


LQ Exclusion Limits -- comparison with LEP and Tevatron

HERA extends the exclusion region

from I. Panagoulias’ talk at DIS2008 – work on PhD / NTUA


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


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


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


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


Isolated leptons + PT miss events


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


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


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


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 ?


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


HERA to LHC

• low x physics at HERA : PDFs forward at LHC

• medium x physics at HERA plateau region at LHC


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.


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


Direct Measurement of FL

x – averaged FL as a function of Q2 : consistent with QCD prediction

FIRST

PRELIMINARY


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


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


LEP2HERA

Tevatron

LHC

ILC

Desert ?

New Physics ?


Backup Slides


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.


D* p resonance in 3 GeV region- Pentaquark

Katja Kruge talk – DIS08


K. Kruge- DIS08

hep2008-olympiath. d. papadopoulou1 neda, the unique river with a feminine name ! theodora d....

Documents

hera ep

papadopoulououtline

hera iith

zeus hera limits

ee polarisation detector

lepton search hera

polarized ee beam

polarized e beams polarization