A n Experiments Krishna Kumar Stony Brook University The - - PowerPoint PPT Presentation

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A n Experiments Krishna Kumar Stony Brook University The - - PowerPoint PPT Presentation

Jul 25, 2023 309 likes •593 views

Acknowledgements: D. Armstrong, M. Dalton, K. Paschke, J. Mammei, M. Pitt, B. Waidyawansa and all my theory colleagues A n Experiments Krishna Kumar Stony Brook University The Electroweak Box Workshop at ACFI, UMass, Amherst, September 28, 2017

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An Experiments

Krishna Kumar Stony Brook University

Acknowledgements: D. Armstrong, M. Dalton, K. Paschke, J. Mammei, M. Pitt, B. Waidyawansa and all my theory colleagues

The Electroweak Box Workshop at ACFI, UMass, Amherst, September 28, 2017

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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

Outline

  • Brief motivation for An measurements
  • Strange quark form factor experiments
  • An in elastic electron-nuclear scattering
  • An from electron-electron scattering
  • Concluding remarks

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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

Parity Violating Electron Scattering

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(gAegVT +β gVegAT)

gV is a function of sin2θW

Weak Charge QW

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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

Parity Violating Electron Scattering

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(gAegVT +β gVegAT)

gV is a function of sin2θW

Weak Charge QW

  • sub-part per billion statistical

reach and systematic control

  • sub-1% normalization control

Variety of Physics Topics:

continuous interplay between hadron physics and electroweak physics

State of the Art

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100% 10% 1% 0.1% G0 G0 E122 Mainz-Be MIT-12C SAMPLE H-I A4 A4 A4 H-II H-He E158 H-III PVDIS-6 PREX-I PREX-II CREX Qweak SOLID MOLLER MESA-P2 MESA-12C ILC-Moller

Pioneering Nuclear Studies (1998-future) S.M. Study (2003-2012) S.M. Design/Planning S.M. Future

PV

A

)

PV

(A δ

Steady improvements in accelerator and detector technology

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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

Experimental Technique

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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

Experimental Technique

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Symmetry of the apparatus helps systematic control:

Acorr = Adet - AQ + α ΔE+ Σβi Δxi

Symmetric azimuthal coverage: Up cancels down, right cancels left…

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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

The An Systematic

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Assumption on previous page: perfect longitudinal polarization

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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

PV Experiments

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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

SAMPLE at MIT-Bates

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SAMPLE data Wells et al., PRC (2001)

tot (N + p N)

p N (inelastic)

N (elastic)

Diaconescu & Ramsey-Musolf (2004)

SAMPLE data

  • S. Wells et al. (2001)

GMs, (GA) at Q2 = 0.1 GeV2

  • pen geometry,

integrating

Pasquini & Vdh (2004)

Proton Target 200 MeV Archival Plots

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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

G0 at JLab

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e- beam

target

CED + Cerenkov

FPD

Proton Target

Forward angle: recoiling proton detected Backward angle: Electrons and Pions detected

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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

G0 Neutron (from 2H)

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  • J. Mammei
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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

PVA4 at Mainz

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GEs + 0.23 GMs at Q2 = 0.23 GeV2 GEs + 0.10 GMs at Q2 = 0.1 GeV2 GMs, GAe at Q2 = 0.1, 0.23, 0.5 GeV2

Recent publication

Precise backward angle measurements Both 1H and 2H

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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

G0 Inelastic Scattering

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Backward angle measurements have the ability to tag electrons and pions, and there are bins dominated by inelastic electrons

  • C. Capuano

Ph.D. Thesis, William and Mary

1H 2H

Bn less than few x 10-5

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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

G0 Pion Production

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  • J. Mammei
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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

Very Forward Angle Measurements: HAPPEX/PREX (Hall A) and Qweak (Hall C)

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Relationship between photo production cross-section and forward scattering amplitude works well when q/E → 0

Elastic Inelastic

detector

Dipole Quad target pure, thin 208Pb target

~10 cm

hardware resolution: ∆p/p ~ 10-3

Septum Magnet

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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

HAPPEX/PREX Data

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theory prediction works remarkably well for light nuclei work by A. Afanasev, M. Gorchstein and collaborators Prediction fails dramatically for 208Pb

Any relevance for precision calculations of gamma-Z boxes for e-N scattering predictions?

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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

QWeak

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right column obsolete

  • B. Waidyawansa

Talks by W. Deconinck and J. Dowd

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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

Measuring An from 12C at Mainz-A1

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Future: could use other targets (28Si, 40Ca, 208Pb) 210-570 MeV beam energies, 15o-25o scattering angles

elastic peak is well-separated in precision spectrometers raw data is uncorrelated between left/right spectrometers: very quiet beam!

Michaela Thiel, Anselm Esser, A1 collaboration

spectrometer B spectrometer A

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. 1 . 2 . 3 . 4 . 5 . 6 T r a n s v e r s e B e a m A s y m m e t r y [ p p m ] Q

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G e V

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c h t e i n e t a l . ] P R E X(EBeam = 1 - 3 GeV)

(570 MeV)

Preliminary

Very Preliminary

  • A. Esser, ECT*

Trento, August’16.

(Forward Direction)

d e t e c t

  • r

s

  • K. Paschke
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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

E158: Electron-Electron (Møller) Scattering

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~ 11 ppb raw statistical error at highest Ebeam, ~ 0.4% error on weak mixing angle

Apart from longitudinal running, transversely polarized electron beam data was collected Hydrogen Target

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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

E158 Transverse Data

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Fig 2: Run2 46GeV Asymmetries vs Channel

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Dixon and Schreiber (2004)

Bn(max) ~ 7 ppm

E158 acceptance: dotted lines

Result: -7.03 ± 0.25 ± 0.36 ppm Theory: -6.91 ppm An must vanish at 90 degrees in the COM for Møller scattering

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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

E158 unpublished data might be interesting for phenomenology

  • The e-p vector analyzing power is found to be

consistent with a dispersive approach prediction assuming that the asymmetry of the 30% inelastic background is zero

  • APV for e-p scattering is found to be consistent

with what is expected from the dominant inelastic scattering amplitude (similar to the inelastic scattering measurements done by G0, PVDIS and Qweak at JLab)

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“Odd” MOLLER Acceptance

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MOLLER proposed to do factor of 5 better than E158

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Why Interesting Here?

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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

Precision Test Planned for MOLLER

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  • set up for physics running
  • convert to vertical polarization

at polarized source

  • run a few hours
  • back to longitudinal

polarization

  • back off beam energy by 50

MeV: horizontal polarization on target

  • extract vector analyzing power

to precision and accuracy of around or better than 0.5%

demonstrate complete understanding of apparatus: simultaneous test of beam polarization, radiative corrections, detector acceptance, backgrounds

Is theory good to 0.1% with Dixon/Schreiber work?

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Beam Normal Asymmetry Measurements Krishna Kumar, September 28, 2017

Concluding Remarks

  • There is a wealth of An measurements from the parity violation experiments on

forward and backward angle elastic electron-proton scattering

  • Some additional An measurements of electron-proton inelastic scattering might be
  • f interest; new data forthcoming from Qweak
  • An measurements on heavier nuclei provides an interesting theoretical challenge:

any new insights relevant to electroweak boxes on light nuclei/proton? New data will soon become available both at 1 GeV (Qweak) and lower energies (Mainz A1)

  • There are already some interesting constraints on the neutral current amplitude in

inelastic electron proton scattering: have all the available data been used to reduce gamma-Z box uncertainties?

  • The future holds many possibilities for providing precision measurements of APV in

inelastic electron proton scattering at a variety of kinematic points: MOLLER, SOLID and P2. How useful will they be? These experiments are all capable of making new An measurements: what’s interesting?

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Continued dialog is necessary to make best use of existing results and optimizing the future program of auxiliary measurements