•　 Report on fitting new data on e- NC polarised

•　 Electroweak NC couplings: au ad vu vd

ZEUS EW fits-report request for preliminary6th Aug 2007

A.M.Cooper-Sarkar and C. Gwenlan – team-1

S. Shimizu and K.Nagano– team -2

Introduction

Status @ DIS06 preliminary HERA II data: 04/05 CC and 04/05 NC (DIS06 prel.) – polarized e-

• First fit including HERA-II data: ZEUS-Pol fit• Fits with free EW parameters

– Mw, GF

– au, ad, vu, vd: 2-param. free fits

Fits with SM formalism (T, sin2thw)

Updates for today Fits were performed on

• ZEUS-JETS data• 04/05 CC (DIS06 prel.) • 04/06 NC (DIS07 prel.)

1. Update of ZEUS-Pol fit.

2. au, ad, vu, vd: 4-EW param. free in addition to PDF parameters

New NC e- data with –ve

polarisation P= -0.27

Lumi=105 pb-1± 3.5%

New NC e- data with +ve

polarisation P= +0.30

Lumi=71.8 pb-1± 3.5%

Req

uest

pre

limin

ary

Updated fit: Newly included NC cross sections

PDFs from the new fit compared to published ZEUS-JETS fit

– central values of the PDFs hardly change at all…..

Req

uest

pre

limin

ary

Updated Fits: PDFs

Req

uest

pre

limin

ary

Updated Fit: Fractional uncertainties

BUT the PDF uncertainties are reduced at high-x, particularly for xuv …..as expected since NC and CC e- cross-sections are both u dominated

PDF fits with NC 04/06 data are not a lot different than what you saw in 2006 with NC 04/05 data

Improvement in uncertainty remains up to high scales- important for LHC

physics!

Fractional Uncertainties at high-Q2

e

Req

uest

pre

limin

ary

Team 2 analysis check (ZMVFN)

Summary so far

Nice improvement to PDF accuracy for high-x u valence

Not dramatically different from 2006

But now we move on to fits with EW parameters free as well as PDF parameters

In 2006 we could only free 2 NC coupling parameters at once because we fell into a double minimum with 4-EW parameters free--- The extra 05/06 NC data has resolved this problem.

We would like to have preliminary status on these new EW fit results with 4-NC couplings free

We don’t want to issue new results with only 2-NC couplings free..but these are in extras, if you are curious

Now consider fits to electroweak NC couplings as well as PDF parameters

　F20 = Σi Ai

0(Q2) [xqi(x,Q2) + xqi(x,Q2)]

xF30= Σi Bi

0(Q2) [xqi(x,Q2) - xqi(x,Q2)]

Ai0(Q2) = ei

2 – 2 ei vi ve PZ + (ve2+ae

2)(vi2+ai

2) PZ2

Bi0(Q2) = – 2 ei ai ae PZ + 4ai ae vi ve PZ

2

Quark couplings to Z

The unpolarised cross-section is given by σ0 = Y+ F20 + Y- xF3

0

The polarised cross-section is given by σP = Y+ F2P + Y- xF3

P

PZ >> PZ2 (γZ interference is dominant)

ve is very small (~0.04).unpolarized xF3 ai,polarized F2 vi

The total cross-section : σ = σ0 + P σP

)(2sin

122

2

2 QM

QP

ZZ

F2P = Σi Ai

P(Q2) [xqi(x,Q2) + xqi(x,Q2)]

xF3P= Σi Bi

P(Q2) [xqi(x,Q2) - xqi(x,Q2)]

AiP(Q2) = 2 ei vi ae PZ - 2 ve ae (vi

2+ai2) PZ

2

BiP(Q2) = 2 ei ai ve PZ - 2 ai vi (ve

2+ae2) PZ

2

au ad vu vd

SM value 0.5 -0.5 0.196 -0.346

4 EW param.

ZO ZMVFN

0.53±0.09±0.13 -0.57±0.31±0.10 0.07±0.10±0.06 -0.56±0.22±0.10

ZJets ZMVFN

0.54±0.10±0.15 -0.52±0.37±0.18 0.06±0.10±0.07 -0.61±0.21±0.13

ZJ RTVFN 0.51±0.10±0.17 -0.54±0.32±0.18 0.05±0.09±0.05 -0.64±0.20±0.14

Team-2

ZO ZMVFN

0.54±0.09±0.13 -0.56±0.32±0.12 0.07±0.10±0.05 -0.58 ±0.22±0.12

Team-2

ZJ ZMVFN

0.54±0.10±0.11 -0.53±0.37±0.19 0.06±0.10±0.07 -0.62 ±0.23±0.15

Team-2

ZJ RTVFN

0.50±0.10±0.12 -0.54±0.37±0.17 0.04±0.09±0.04 -0.67 ±0.20±0.14

OLD 2006 ZO ZMVFN

0.64±0.15±0.19 0.04±0.61±1.01 0.13±0.17±0.22 -0.47±0.39±0.65

Request preliminary

Fits with ai, vi free as well as PDF parameters

SM formalism ai = T3i , vi = T3i – 2ei sin2ƏW

Request preliminary

au/vu ad/vd au/ad vu/vd contours (RTVFN, ZJ)

Comparison to the previous fit DIS06

Used to have a double minimum

when 4-EW parameters free.

The new NC data from 05/06 has resolved this

Team-2 contours (RTVFN, ZJ)

total uncert.

central value

vd moves away from SM value, but this is only a 68% CL contour

Comparison with other experiments

Request preliminary

Conclusions

Very nice electroweak results Good agreement between two analyses. Lets go for preliminary at Lepton-Photon 07

CC e- data with –ve polarisation P= -0.27

Lumi= 78.8 pb-1 ± 3.5%

vs fit predictions for ZEUS-JETS fit including these data

CC e- data with +ve polarisation P= 0.33

Lumi=42.7pb-1 ± 3.5%

vs fit predictions for ZEUS-JETS fit including these data

CC vs Updated ZEUS-Pol Fit

PDFs are stable with free/fixed EW parameters.

a,v-free vs a,v-fixed

Team 2 analysis check (ZMVFN)

ZMVFN scheme 4-EW parameter contours from Team-2 (ZJ and ZO)

ZMVFN scheme 2-EW parameter contours from Team-2 (ZJ and ZO)

These 2-EW parameter contours can be compared with those issued in 2006. they are compatible but not identical