21 July 2008 PREX Integrating Detector: Assessment and Plans 1

Parity-Violating Møller Scattering

Introduction and Meeting GoalsKrishna Kumar

University of Massachusetts, Amherst

August 14, 2008

Møller Meeting

Jefferson Laboratory

APV = !mEGF"2!"

16 sin2 !(3 + cos2 !)2

QeW

21 July 2008 PREX Integrating Detector: Assessment and Plans

Møller Scattering

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Purely leptonic reaction

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APV ∝meElab (1− 4sin2ϑW )

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σ ∝1Elab

Figure of Merit rises linearly with Elab

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δ(sin2ϑW )sin2ϑW

≅ 0.05δ(APV )APV

Small, well-understood dilution

SLAC: Highest beam energy with moderate polarized luminosityJLab 11 GeV: Moderate beam energy with LARGE polarized luminosity

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Comprehensive Search for New Neutral Current Interactions

Many new physics models give rise to non-zero Λ’s at the TeV scale: Heavy Z’s, compositeness, extra dimensions…

One goal of neutral current measurements at low energy AND colliders: Access Λ > 10 TeV for as many f1f2 and L,R combinations as possible

Important component of indirect signatures of “new physics”

LEPII, Tevatron access scales Λ’s ~ 10 TeVe.g. Tevatron dilepton spectra, fermion pair production at LEPII

- L,R combinations accessed are parity-conservingLEPI, SLC, LEPII & HERA accessed some parity-violating combinations but precision dominated by Z resonance measurements

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Lf1 f2=

4πΛ ij2 ηij

i, j= L ,R∑ f 1iγµ f1i f 2 jγ

µ f2 j

Consider

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f1 f 1→ f2 f 2

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f1 f2 → f1 f2orΛ’s for all f1f2 combinations and L,R combinations

Eichten, Lane and Peskin, PRL50 (1983)

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Colliders vs Low Q2

Window of opportunity for weak neutral current measurements at Q2<<MZ2

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Processes with potential sensitivity: - neutrino-nucleon deep inelastic scattering - Atomic parity violation - parity-violating electron scattering

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E158 New Physics Reach

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APV ≈ −4 ×10−9 × Ebeam × Pbeam

•~ 10 ppb statistical error at highest Ebeam

•~ 0.4% error on weak mixing angle

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E158 Result

45 GeV: 14.0 revsg-2 spin precession

48 GeV: 14.5 revs

APV = (-131 ± 14 ± 10) x 10-9

Phys. Rev. Lett. 95 081601 (2005)

!+ee

!!ee

Z!

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Physics Implications

0.001 0.01 0.1 1 10 100 1000

Q [GeV]

0.225

0.230

0.235

0.240

0.245

0.250

APVCesium

SLAC E158Moller

NuTeV

!-DIS

Z-pole

sin

2W

Z"

> (M )

Erler and Ramsey-Musolf (2004) > 7 TeV

> 16 TeV

> 1 TeV

0.231

0.232

0.233

83.6 83.8 84 84.2

68! CL

!ll "MeV#

sin

2"

lep

t

eff

mt= 172.6 $ 1.4 GeV

mH= 114...1000 GeV

mt

mH

#$

March 2008

15 May 2008 Probing the TeV-Scale with Parity-Violating Electron Scattering

Electroweak Constraints

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15 May 2008 Probing the TeV-Scale with Parity-Violating Electron Scattering 9

Precision sin2θW at Any Scale

⇒ mH = 89 +38-28 GeV⇒ S = -0.13 ± 0.10

ALR AFB (Z→ bb)

sin2θw = 0.2310(3)

↓mH = 35 +26-17 GeV

S= -0.11 ± 17

sin2θw = 0.2322(3)

↓mH = 480 +350-230 GeV

S= +0.55 ± 17

Rules out the SM! Rules out SUSY!Favors Technicolor!

Rules out Technicolor!Favors SUSY!

(also APV in Cs) (also Moller @ E158)

W. Marciano

The Average: sin2θw = 0.23122(17)

3σ apart

•Precision sin2θW measurements at colliders very challenging•Neutrino scattering cannot compete statistically•No resolution of this issue in next decade

slide adapted from C. Kolda

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Møller Scattering at 11 GeVParity-Violating Møller Scattering:Luminosity and Stability at Jlab upgrade makes feasible a factor of 5 improvement over E158

sin2θW to ± 0.00025Λee ~ 25 TeV reach

Best new measurement until Linear Collider or Neutrino Factory

E158-like Quad concept: same quads provide focus; fits within 25 m

A possible toroid design with better acceptance is being investigated

L. Mercado

δ(Aexp) = 0.6 ppb!

Rate ~ 200 GHz!

Mother of all PV measurements!

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Constraining New PhysicsDoes Supersymmetry (SUSY) provide a candidate for dark matter?•Neutralino is stable if baryon (B) and lepton (L) numbers are conserved•B and L need not be conserved (RPV): neutralino decay

Kurylov, Ramsey-Musolf, SuRPC SUSY

RPV SUSY

Qweak

12 GeV Møller

12 GeV Møller

PVDIS

Qweak, PVDIS and Møller measurements are complementary

Model-dependent constraints on new particles:• e.g. Z’ bosons ~ 2.5 TeV• Should LHC see anomalies, such measurements extremely valuable

15 May 2008 Probing the TeV-Scale with Parity-Violating Electron Scattering

Community Endorsement

• 12 GeV Science Review • Well-attended workshop Dec ‘06• High profile in Long Range Plan• Steering Committee formed:

– R. Carlini, G. Cates, K. Kumar, D. Mack, P. Souder, W. van Oers

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15 May 2008 Probing the TeV-Scale with Parity-Violating Electron Scattering 13

E158 Design ~ 1997• 10 nm control of beam centroid on target

– R&D on polarized source laser transport elements

• 12 microamp beam current maximum– 1.5 meter Liquid Hydrogen target

• 20 Million electrons per pulse @ 120 Hz– 200 ppm pulse-to-pulse statistical fluctuations

• Electronic noise and density fluctuations < 10-4

• Pulse-to-pulse monitoring resolution ~ 1 micron• Pulse-to-pulse beam fluctuations < 100 microns

– 100 Mrad radiation dose from scattered flux• State-of-the-art radiation-hard integrating calorimeter

• Full Azimuthal acceptance with θlab ~ 5 mrad– Quadrupole spectrometer

• Novel design that enclosed primary & scattered beam inside magnets

– Complex collimation and radiation shielding issues• Precision alignment, water cooling and radiation protection

21 July 2008 PREX Integrating Detector: Assessment and Plans

11 GeV JLab Challenges

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• 1 nm control of beam centroid on target– R&D on polarized source laser transport elements

• 85 microamp beam current maximum– 1.5 meter Liquid Hydrogen target: 5-6 kW!!

• 200 GHz Rate– Must flip Pockels cell ~ 1 kHz: more R&D needed

– 50 ppm pulse-to-pulse statistical fluctuations• Electronic noise and density fluctuations < 10-5

• Pulse-to-pulse monitoring resolution ~ 100 nm!

• Full Azimuthal acceptance with θlab ~ 5 mrad– aggressive spectrometer design

• Quadrupole design a la E158• New 100% azimuthal acceptance toroids

– Complex collimation and radiation shielding issues• Precision alignment, water cooling and radiation protection

21 July 2008 PREX Integrating Detector: Assessment and Plans

Statistical Error Critical

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21 July 2008 PREX Integrating Detector: Assessment and Plans

Progress to Date

• Spectrometer Design– Quadrupole

• proof of principle• first attempt at detector placement and collimation

– Toroids• novel 100% acceptance• first attempt at ray traces and field characteristics

• Spectrometer choice drives everything else

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21 July 2008 PREX Integrating Detector: Assessment and Plans

Near-Term Plans• Run simulations on two spectrometer

options:– Collimation– Backgrounds– Statistical Error

• Initiate formation of collaboration• Assign tasks for LOI/Proposal

preparation

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21 July 2008 PREX Integrating Detector: Assessment and Plans

Meeting Goals

• Lay out technical challenges• Assign tasks to address them• Estimate statistical error• LOI or Proposal?• Timeline for document• Next meeting?

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