HERA-II results on inclusive cross-sectionsA .M. Cooper-Sarkar

Oxford

On behalf of ZEUS and H1 at the low-x workshop, Lisbon 2006

•Neutral Current (NC) and Charged Current (CC) single and double differential cross sections from ’03-’05 running with polarised e+ and e- beams

•Polarisation dependence of cross-sections

•Limits on MWR

•Extraction of xF3

•New PDF fit- reduced high-x uncertainties

•Fits for electroweak parameters:

MW, GF,, g

au,vu,ad,vd,

T3u,T3

d, sin2θW, T3uR,T3

dR

kp

qpy

qp2

Qx

)'kk(qQ2

222

: virtuality of exchanged boson

: Bjorken x

: inelasiticity

Kinematic variables

New data with polarised lepton beams for both Neutral Current (NC) and Charged Current (CC) processes

Pe >0

ZEUS

Pe <0

ZEUS

Pe >0

H1

Pe <0

H1

e+

03-04

+0.32±0.01

L=12.3 pb–1

–0.41±0.01

L=11.5 pb–1

+0.33±0.01

L=26.9 pb–1

–0.40±0.01

L=20.7 pb–1

e-

04-05

+0.33±0.02

L=42.7 pb–1

–0.27±0.01

L=78.8 pb–1

+0.37±0.02

L=29.6 pb–1

–0.27±0.01

L=68.6 pb–1

-- e+p cross sections have been published. ZEUS hep-ex 0602026: H1 Phys Lett B634 (2006) 173

-- e–p analyses (preliminary)

New data with polarised beams

The data has been used for new fits to improve our knowledge of parton distributions (PDFs) and electroweak parameters

First Charged Current results

(At leading order LO)

e+p CC cross section (hep-ex 0602026) e–p CC cross section (ZEUS preliminary)

Both for e+p and e–p, measured cross sections from different polarisations have the same shape.Only their scales are different.Consistent with SM prediction =>

)x,Q(2

P1)x,Q( 2

LHCCe2pe

pol

ZEUS: polarisation dependence of e+ and e-

H1: dependence of cross-section on charge of lepton

pb.)sys(.)stat(3.14.87 6.25.2

peCC

pb.)sys(.)stat(3.17.46 5.13.1

peCC

<Pe>=–0.27±0.01

<Pe>=+0.33±0.02

<Pe>=–0.27±0.01

<Pe>=+0.37±0.02

H1 (Q2 > 400 GeV2)

бe-p = 70.4 ± 1.2(stat.) ± 3.1(sys) pb

бe-p = 34.5 ± 1.4(stat.) ± 1.5(sys) pb

Consistent with SM – the limit on RHCC cross-section corresponds to 95% CL on mass of WR boson, MWR>180 GeV ZEUS: MWR>186 GeV H1

(Q2 > 200 GeV2)

Cross sections were meausured as a function of Pe.

Linear relation between cross section and polarisation is clearly shown.

ZEUS preliminary

Now Neutral Current Results

-y2FLo/p

At leading order (LO)

H1

dб/dQ2 e+p RH,LH and RH/LH

Positron single differential cross-sections

dб/dQ2 e- p RH,LH and RH/LH

H1Electron single differential cross-sections

H1 б(Unpolarised) H1 xF3

ZEUS also has preliminary results on polarised double differential cross-sections for both CC and NC processes- these are shown with a new PDF fit ZEUS-pol.

ZEUS also has preliminary results on polarised double differential cross-section for both CC and NC processes- these are shown with a new PDF fit ZEUS-pol

So what is this new PDF fit? ZEUS-pol

It is done with exactly the same formalism as the published ZEUS-JETS fit (Eur.Phys.J.C42(2005)1) -but adding in the double differential cross-sections for NC and CC data from 121 pb-1 of the new HERA-II e-p ‘05 polarised data

Expected since NC and CC e- are dominantly sensitive to u quark

Precision of xuv now approaches that of global fits using fixed target data

ZEUS have also made an analysis varying the electroweak parameters simultaneously with the PDF parameters within the same fit formalism

-y2WL(x,Q2)

This was from the shape of CC dб/dQ2

This was from a similar PDF+EW analysis on HERA-I H1 data

Let the neutral current axial vector and vector couplings au,vu,ad,vd be free

These results are best displayed as contour plots

Compare to the red contours determined in the same way – BUT without polarised data

Improvement in the vector couplings as expected from polarised F2 data

Compare the result with those from other experiments

H1 analysis of HERA-I data

LEP and CDF analyses

In fact for DIS data the sensitivity to the couplings is through γ/Z interference to the axial vector couplings (from xF3

0) and vector couplings (from F2P) separately – not to

the combinations ( a2+ v2) which LEP and CDF data access through the Z - so we plot the axial and vector contours separately

The improvement in the vector couplings with polarised data is striking

We can also make fits within the standard model formalism

OR we can extend the standard model formalism with right handed isospin

Summary

•New data on Neutral Current (NC) and Charged Current (CC) single and double differential cross sections from ’03-’05 running with polarised e+ and e- beams

•Polarisation dependence of cross-sections in agreement with Standard Model

•Limits on MWR: MWR>180 GeV ZEUS: MWR>186 GeV H1

•Extraction of xF3

•New PDF fit- reduced high-x uncertainties- particularly for xuv

•Fits for electroweak parameters: MW – best measurement for space-like process

GF,, - at high scale Q2 ~400 GeV2

vector and axial vector NC couplings: au,vu,ad,vd,

T3u,T3

d, sin2θW, T3uR,T3

dR

In agreement with Standard Model – best measurements using light quarks