Neutral current deep inelastic scattering in zeus
This presentation is the property of its rightful owner.
Sponsored Links
1 / 14

Neutral Current Deep Inelastic Scattering in ZEUS PowerPoint PPT Presentation


  • 98 Views
  • Uploaded on
  • Presentation posted in: General

Neutral Current Deep Inelastic Scattering in ZEUS. Ricardo Gonçalo Imperial College. The HERA collider NC Deep Inelastic Scattering at HERA The ZEUS detector Neutral current cross section measurement Some ZEUS structure functions results Conclusions and outlook.

Download Presentation

Neutral Current Deep Inelastic Scattering in ZEUS

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Neutral current deep inelastic scattering in zeus

Neutral Current Deep Inelastic Scattering in ZEUS

Ricardo Gonçalo

Imperial College

The HERA collider

NC Deep Inelastic Scattering at HERA

The ZEUS detector

Neutral current cross section measurement

Some ZEUS structure functions results

Conclusions and outlook


Neutral current deep inelastic scattering in zeus

HERA and the ZEUS detector

1996-1997 running:

 820 GeV protons

 27.5 GeV positrons

 Integrated luminosity 38.6 pb-1

1998-1999running:

 920 GeV protons

 27.5 GeV electrons

 Integrated luminosity 16.6 pb-1

1999-2000running:

 920 GeV protons

 27.5 GeV positrons

 Integrated luminosity 66.0 pb-1

Bunch crossings every 96ns

Centre of mass energy:

s = 318 GeV (98/00) 300 GeV (92/97)

IoP HEPP Conference, Southampton, 3-5 April 2001


Deep inelastic scattering at hera

Deep Inelastic Scattering at HERA

Kinematic variables:

Q² four momentum transfer

x Bjorken scaling variable

y inelasticity

Only 2 independent variables:

Q2 = x.y.s

(s is the c.m. energy)

e (k)

e (k’)

,Z0 (Q2=-q2)

X (P’)

p (P)

xF3parity violating

FL negligible at high Q2

Leading order cross section:

with:

Our aim: to determine the proton structure through the measurement of the proton structure functions

IoP HEPP Conference, Southampton, 3-5 April 2001


Neutral current deep inelastic scattering in zeus

HERA and the ZEUS detector

Depleted uranium compensating calorimeter:

 99.7% solid angle coverage

 Timing resolution < 1ns (E>4.5 GeV)

 Energy resolution (test beam)

electrons

protons

Central Tracking Detector (CTD)

 Angular acceptance 15o<<164o

 r- resolution  230 m

y

Magnetic field of 1.43 T achieved with thin superconducting solenoid

z

x

IoP HEPP Conference, Southampton, 3-5 April 2001


Neutral current cross section measurement

Neutral current cross section measurement

  • Offline selection cuts:

  • Find the electron

  • Vertex within: -50 < Zvtx < 50 cm

  • Scattered electron cuts:

  • Electron energy: Ee > 10 GeV

  • Electron isolation

  • Within CTD acceptance:

  •  Electron track momentum > 5 GeV

  •  Track and cluster matching

  • Forward electrons: PT,e > 30 GeV

  • Total transverse momentum should be small: PT,tot < 4ET,tot

  • Background cut: 38 <  < 65 GeV,

  • with:

IoP HEPP Conference, Southampton, 3-5 April 2001


Neutral current cross section measurement1

Neutral current cross section measurement

Low Q2:

 exchange

 similar cross sections for e-p and e+p

High Q2:

 and Z0 exchange plus interference term

 cross sections greater for

e-p (d/dQ2 xF3) than for

e+p (d/dQ2 -xF3)

IoP HEPP Conference, Southampton, 3-5 April 2001


Neutral current deep inelastic scattering in zeus

Why measure F2?

 F2 sensitive to valence and sea quarks

 All flavors contribute to F2

 Gluon density can be extracted from d F2 /dlnQ2

IoP HEPP Conference, Southampton, 3-5 April 2001


How to measure f 2 em

How to measure F2em ?

  • Start by measuring Neutral Current reduced cross section

  • Cross section has contributions from  and Z0 exchange and their interference(at high Q2, reduced cross section falls for e+p data and rises for e-p data)

  • Apply corrections to get F2from R

Reduced cross section:

IoP HEPP Conference, Southampton, 3-5 April 2001


Why measure xf 3

Why measure xF3?

xF3 sensitive to valence quarks only

Sea quarks created in pairs

=> (quark-antiquark)=0

And How?

IoP HEPP Conference, Southampton, 3-5 April 2001


First xf 3 measurement from zeus

First xF3 measurement from ZEUS

  • First direct look at valence quarks at high Q2

  • Yellow band is the calculated FLmultiplied by 10

  • Measurement used e+p data from 1996-97 (c.m. energy of 300 GeV) and e-p data from 1998-99 (c.m. energy of 318 GeV) => corrections necessary

IoP HEPP Conference, Southampton, 3-5 April 2001


Conclusions and outlook

Conclusions and outlook

 Present Neutral Current results from ZEUS are systematics limited up to Q2 800 GeVbut there is room for improvement for higher Q2 using the currently available data.

 Neutral current cross sections will be measured at high Q2using data from 1998/99 (e-p) and 1999/00 (e+p)with s = 318 GeV.

 Measurement of F2 and xF3 can be made with available data.

Outlook

  • Lepton beam polarization after the 2000/2001 shutdown and high luminosity expected (1 fb-1 until 2006).

  • Improved tracking (new vertex detector and forward tracking)

  • This will allow:

  •  Setting limits for the mass of W-R, W+L, using Charged Current measurements,

  •  The direct measurement of weak couplings to quarks u and d.

  •  Possibility of lower systematic errors for lepton tagging in fwd region.

  •  Charm tagging.

IoP HEPP Conference, Southampton, 3-5 April 2001


Neutral current deep inelastic scattering in zeus

My neutral current cross section measurement

  • Only d/dQ2 so far

  • Statistical errors only

  • Analysis of 1998/99 e-p data and 1999/00 e+p data going in parallel

  • Still a lot of work to be done...

IoP HEPP Conference, Southampton, 3-5 April 2001


Luminosity upgrade and polarisation

Luminosity upgrade and polarisation

Charged Current: cross section linear on polarisation.

Limits or measurement of mass of W-R, W+L

Neutral current: 4 different x-sections will allow measurement of couplings au, vu, ad, and vd (HERA sensitive to u & d; LEP sensitive to c & b)

IoP HEPP Conference, Southampton, 3-5 April 2001


Neutral current deep inelastic scattering in zeus

xF3 from H1

Luminosity upgrade and polarisation

With both lepton flavors and polarizations  4 different cross sections

xF3 measurement from H1: different binning

IoP HEPP Conference, Southampton, 3-5 April 2001


  • Login