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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
2
Purely leptonic reaction
€
APV ∝meElab (1− 4sin2ϑW )
€
σ ∝1Elab
Figure of Merit rises linearly with Elab
€
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
15 May 2008 Probing the TeV-Scale with Parity-Violating Electron Scattering 3
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
€
Lf1 f2=
4πΛ ij2 ηij
i, j= L ,R∑ f 1iγµ f1i f 2 jγ
µ f2 j
Consider
€
f1 f 1→ f2 f 2
€
f1 f2 → f1 f2orΛ’s for all f1f2 combinations and L,R combinations
Eichten, Lane and Peskin, PRL50 (1983)
15 May 2008 Probing the TeV-Scale with Parity-Violating Electron Scattering 4
Colliders vs Low Q2
Window of opportunity for weak neutral current measurements at Q2<<MZ2
2
Processes with potential sensitivity: - neutrino-nucleon deep inelastic scattering - Atomic parity violation - parity-violating electron scattering
15 May 2008 Probing the TeV-Scale with Parity-Violating Electron Scattering 5
E158 New Physics Reach
€
APV ≈ −4 ×10−9 × Ebeam × Pbeam
•~ 10 ppb statistical error at highest Ebeam
•~ 0.4% error on weak mixing angle
15 May 2008 Probing the TeV-Scale with Parity-Violating Electron Scattering 6
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!
15 May 2008 Probing the TeV-Scale with Parity-Violating Electron Scattering 7
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
15 May 2008 Probing the TeV-Scale with Parity-Violating Electron Scattering 10
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!
15 May 2008 Probing the TeV-Scale with Parity-Violating Electron Scattering 11
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
12
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
14
• 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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