Low Energy Tests of
Download
1 / 69

Low Energy Tests of the Standard Model - PowerPoint PPT Presentation


  • 116 Views
  • Uploaded on

Low Energy Tests of the Standard Model. * PAST. * PRESENT. * FUTURE. Emlyn Hughes Spin 2004 Trieste October 14, 2004. Electroweak Mixing Angle. e = g sin q w. Characterizes the mixing between the weak and EM interaction in the electroweak theory. 2. M w. 2. sin 2 q w = 1 -. M z.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Low Energy Tests of the Standard Model' - britain


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

Low Energy Tests of

the Standard Model

* PAST

* PRESENT

* FUTURE

Emlyn Hughes

Spin 2004

Trieste

October 14, 2004


Electroweak Mixing Angle

e = g sinqw

Characterizes the mixing between the weak and EM

interaction in the electroweak theory

2

Mw

2

sin2qw = 1 -

Mz


3 Types of Measurements

* Electron scattering (parity violation)

* Atomic parity violation

* Neutrino physics (NC/CC cross section)


Parity Violation in

Polarized Electron Scattering

e-

e-

e-

e-

g

Z

unpolarized quarks or electrons or protons

Parity conserving

Parity violating


Parity Violation in the Electroweak Theory

R

L

s - s

APV =

R

L

s + s

g2

2

+ q2

AW

mZ

2AW AEM

PV

2

~

2

~

~

A

AEM

2

2

+

e2

AW

AEM

q2

PV

q2

A

~

2

2

mZ



End Station A

End Station A


SLAC Parity Experiments

Detector

e-

Target

High

Energy

(unpolarized)

R

L

s - s

APV =

Parity-violating asymmetry

R

L

s + s



Yale E80 Polarized Source




Results on Parity Violation

E80

ALR < 5 x 10-3at Q2 ~ 1.4, 2.7 GeV2

E95

ALR < 3.2 x 10-3at Q2 ~ 4 GeV2

Not sensitive to electroweak mixing

in the Standard Model


First Measurements

of Electroweak Mixing



SLAC E122

Detector

e

16 – 22 GeV

Liquid

Deuterium

GaAs source

High current

30 cm target

Dedicated run


120 Hz

Reversed every

few runs



SLAC E122 waveplate reversal

Parity-violating

asymmetry


SLAC E122 Energy Scan

Parity-violating

asymmetry


SLAC E122 Result

(1978)

sin2qw = 0.224 + 0.020

First definitive measurement of mixing between

the weak and electromagnetic interaction


Atomic Parity Violation

e-

e-

g or Z

p

2

2

mea

LR

q2

-14

A

~

2

~

2

10

~

2

2

mZ

mZ


Experiment

Z3 Law

Heavy Atoms

Theory

PV Signal

sin2qw

Bismuth Z = 83






Neutrino Physics

Bubble

Chamber

Gargamelle


HPWF Neutrino Detector

(Harvard, Pennsylvania, Wisconsin, Fermilab)




(1977)

(1977)

(1975)

(1977)

1978


TODAY...

LEP and SLC e+e- collider

Dsin2qw = 0.00016 (PDG2004)

from Z pole measurements


Status in 1999

sin2qw

~5%

Q (GeV)


SLAC Experiment E158

Detector

e

50 GeV

Liquid

Hydrogen

e-e-

scattering

s - s

APV =

s + s

Without electroweak radiative corrections,

2

m E GF

16 sin q

1

(

)

-

sin2qw

APV

=

2

4

2p 

(3 + cos q)2

In practice:

APV

~

1.5 x 10-7


E158 Collaboration

  • SLAC

  • Smith College

  • Syracuse

  • UMass

  • Virginia

  • UC Berkeley

  • Caltech

  • Jefferson Lab

  • Princeton

  • Saclay

7 Ph.D. Students

60 physicists

Sept 97: EPAC approval

1998-99: Design and Beam Tests

2000: Funding and construction

2001: Engineering run

2002: Physics Runs 1 (Spring), 2 (Fall)

2003: Physics Run 3 (Summer)


Scattering Processes

e-

e-

e-

e-

g

Z

e-

e-

e-

e-

Parity-conserving

Parity-violating

e-

e-

g

g

Background

p

p


Challenges

I. Statistics

II. Beam monitoring & resolution

 jitter vs. statistics

III. Beam systematics

 false asymmetries

IV. Backgrounds


target

Detector

cart

Concrete shielding

Spectrometer magnets

Setup in End Station A


STATISTICS

# electrons per pulse 107

Rep rate (120 Hz) 109

Seconds/day 1014

100 days 1016

DA ~ 10-8



toroid 30 ppm

energy 1 MeV

BPM 2 microns

Agreement (MeV)

BPM24 X (MeV)

Resolution 1.05 MeV

BPM12 X (MeV)

Beam Monitoring Correlations


III. Beam Asymmetries

Polarized

source


SLOW REVERSALS

* Halfwaveplate @ source

~few hours

* 48 vs. 45 GeV energy

~ few days


APV vs. time

ppb



IV. BACKGROUNDS

* electron-proton elastic scattering

* pion production

* radiative inelastic electron-proton scattering

W2 > 3 GeV2

* 2 photon events with transverse polarization

*

*

*




E158 Physics Runs

Run 1: Spring 2002

Run 2: Fall 2002

Run 3: Summer 2003


RUNI

FINAL RESULT

At Q2 = 0.027 (GeV/c)2….

APV= -175  30 (stat)  20 (syst) ppb

MS

sin2  = 0.2293 ± 0.0024 (stat) ±0.0016 (syst)

w

MS

Theory:

sin2  = 0.2311 ± 0.00016

w



All E158 Data

PRELIMINARY

At Q2 = 0.027 (GeV/c)2….

APV= -128  14 (stat)  12 (syst) ppb

MS

sin2  = 0.2330 ± 0.0011 (stat) ±0.0010 (syst)

w

MS

Theory:

sin2  = 0.2311 ± 0.00016

w


Status in 1999

sin2qw

Q (GeV)


Cesium Atomic Parity Violation Result vs. Time

(Colorado measurement)

sin2qw

0.240

Standard Model

0.238

Kuchiev

Flambaum

0.236

Kozlov

Porsev

Tupitsyn

Johnson

Bednyhakov

Soff

0.234

Derevianko

Bennett

Wieman

Dzuba

Flambaum

0.232

Wieman et al.

0.230

2000

1999

1998

2001

2002

2003

1997

Modifications in the theoretical corrections to the

atomic structure


7s

Status Today

sin2qw


E158 Beyond Standard Model Implications...

(95% confidence level)

* Limit on LLL ~ 10 TeV

* Limit on SO(10) Z’ ~ 900 GeV

  • * Limit on lepton flavor

violating coupling ~ 0.01GF


FUTURE:

Low energy polarized electron

scattering

* Jefferson Lab

* SLAC (could do it, but won’t)


The Qweak Experiment:

A Search for New Physics at the TeV Scale Via a Measurement of the Proton’s Weak Charge

December 3, 2001

D. Armstrong1, T. Averett1, J.D. Bowman5, R. Carlini9(contact person), C.A. Davis11

J. Erler3, R. Ent9, M. Finn1, T.A. Forest6, K. Johnston6, R. Jones2, S. Kowalski8, L. Lee7,

A. Lung9, D. Mack9, S.A. Page7, S. Penttila5, M. Pitt10, M. Poelker9, W.D. Ramsay7,

M. Ramsey-Musolf2,4, J. Rochel9, N. Simicevic6, G. Smith9, R. Suleiman8, S. Taylor8,

W.T.H. van Oers7, S. Wells6, S. Wilburn5, S.A. Wood9

1College of William and Mary, Williamsburg, VA

2University of Connecticut, Storrs, Connecticut

3David Rittenhouse Laboratory, University of Pennsylvania, Philadelphia, Pennsylvania

(New address (1/1/2002): Instituto de Fisica, Universidad Nacional Autonoma de Mexico,

01000 Mexico D.F., Mexico)

4Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, California

5Los Alamos National Laboratory, Los Alamos, New Mexico

6Louisiana Tech University, Ruston, Louisiana

7University of Manitoba, Winnipeg, Manitoba, Canada

8Massachusetts Institute of Technology, Cambridge, Massachusetts

9TJNAF, Newport News, VA

10Virginia Polytechnic Institute, Blacksburg, Virginia

11TRIUMF, Vancouver, Canada

Approved January 2002


Jefferson Lab Qweak Experiment

Elastic electron-proton scattering experiment

* 180 mAmp current

* 1 GeV beam

* 2200 hours of data


Submitted: June 2003

SLAC DIS-Parity Letter of Intent

~39 GeV polarized electrons scattering off deuterium target

ALR ~ 10-3 at Q2 ~ 20 GeV2

Measurement to 0.6% precision...


Projected experimental uncertainty from

DIS-parity proposal @ SLAC

and Qweak experiment @ Jefferson Lab


LHC

Not a parity experiment …

 Has major impact on precision low energy tests for

discovery potential

Z’, supersymmetry, compositeness, leptoquarks, etc…

in the TeV range


SUMMARY

* Performed a first measurement

of parity violation in e-e- scattering

Final result publication in ~ 1/2 year

* Future parity experiments active

* Complementary to collider experiments


ad