The MOLLER Project at Jefferson Laboratory
Krishna S. KumarUniversity of Massachusetts, Amherst
Parity-Violating Electron-Electron (Møller) Scattering
K. Kumar The MOLLER Project at Jefferson Laboratory
OutlinePhysics Motivation
• Physics Context★ Low Energy Neutral Current Interactions & TeV Physics
★ Parity-Violating Electron Scattering
• Møller Scattering★ The MOLLER Project at Jefferson Laboratory
★ Physics Reach
Experimental Design• Main Components of the Apparatus
• Statistical & Systematic Errors
Status and Outlook
An ultra-precise measurement of the parity-violating asymmetry in fixed target electron-electron (Møller) scattering
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K. Kumar The MOLLER Project at Jefferson Laboratory
Physics Context
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K. Kumar The MOLLER Project at Jefferson Laboratory
145 150 155 160 165 170 175 180 185 190mt [GeV]
10
20
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50
100
200
300
500
1000
MH [G
eV]
LEP 2
Tevatron excluded (95% CL)
excluded
all data (90% CL)
(95% CL)
ΓZ, σhad, Rl, Rq
Z pole asymmetriesMWlow energymt
courtesy: Jens Erler
Precision EW PhysicsStart with 3 fundamental inputs needed: αem, GF and MZ
Other experimental observables predicted at 0.1% level: sensitive to heavy particles via higher order quantum corrections
4th and 5th best measured parameters: sin2θW and MW
Allows searches for new physics at the TeV scale via
small measurement deviations
All weak neutral current amplitudes are functions of sin2θW
W
W Z
Zt b t t
Muon decay Z production
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K. Kumar The MOLLER Project at Jefferson Laboratory
Colliders AND Low Q2Neutral Current Amplitude at Low & High Energy
Low Q2 Processes with TeV-scale Sensitivity•Parity-violating electron scattering•opposite parity transitions in heavy atoms•Neutrino deep-inelastic scattering
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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
€
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 f2orMany new physics models give rise to such terms:
Heavy Z’s, compositeness, extra dimensions, SUSY…
At colliders, one studies Z boson production and decay
At low energies, one studies neutral weak scattering
Both methods have complementary access to new neutral interactions
at the TeV scale
K. Kumar The MOLLER Project at Jefferson Laboratory
PV Electron Scattering
(gAegV
T +β gV
egAT)
€
10−4 ⋅Q2
€
APV ~ 10−5 ⋅Q2 to gV and gA are function of sin2θW
At very forward angles, APV ∝ gVT, the target vector coupling, called
the weak charge QW
Thumb rule: measure or better to access the multi-TeV scale
!(sin2 "W) ! 0.002
•One of the incident beams longitudinally polarized•Change sign of longitudinal polarization•Measure fractional rate difference
The pioneering experiment was SLAC E122 in the mid-70s: PV Deep-Inelastic Scattering off Liquid Deuterium
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K. Kumar The MOLLER Project at Jefferson Laboratory
-810 -710
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PVeS Experiment Summary
100%
10%
1%
G0
G0
E122
Mainz-Be
MIT-12C
SAMPLE H-I
A4
A4
H-II
H-He
E158
H-III
PV-DIS
PREX
Qweak
(12GeV)PV-DIS
Moller(12GeV)
PVA
)PV
(A!
Rich Physics
•photocathodes, polarimetry, high power cryotargets, nanometer beam stability, precision beam diagnostics, low noise electronics, radiation hard detectors
•Beyond Standard Model•Strange quark form factors•Neutron skin of a heavy nucleus•QCD structure of the nucleon
• part per billion systematic control• 1% normalization control
Parity-violating electron scattering has become a precision tool
Mainz & MIT-Bates in the mid-80s
JLab program launched in the mid-90s: focus on strange quarks
History of attracting & training excellent students & postdocs7
SLACMIT-Bates
MainzJLab
K. Kumar The MOLLER Project at Jefferson Laboratory
Fundamental Symmetries & Nuclear Physics
Direct and Indirect Searches for Physics Beyond the Standard Model
Lower Energy: Q2 << MZ2Large Hadron Collider as well as
A comprehensive search for clues requires:
Compelling arguments for “New Dynamics” at the TeV Scale
Neutrino Physics: 0νββ decay, accelerator/reactor experiments
Rare or Forbidden Processes: EDMs, Violation of CP, T, Lepton Flavor
Dark Matter SearchesPrecision Electroweak Measurements
• weak neutral currents at low energy, muon g-2, weak decays
Topics critically need nuclear experimentalists and theorists 8
K. Kumar The MOLLER Project at Jefferson Laboratory
SLAC E158
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Purely leptonic reaction
LH24-7 mrad
45 & 48 GeV Beam85% longitudinal polarization
Standord Linear Accelerator Center (SLAC) Major technical challenges
Final Result:APV = (-131 ± 14 ± 10) x 10-9
Phys. Rev. Lett. 95 081601 (2005)
16 TeV17 TeV
0.8 TeV 1.0 TeV (Zχ)
0.01•GF
95% C.L.
Limits on “New” Physics
0.001 0.01 0.1 1 10 100 1000µ [GeV]
0.23
0.234
0.238
0.242
0.246
sin
2!
W(µ
)
QW
(APV)Q
W(e)
"-DIS
LEP 1
SLC
Tevatron
e-DIS
MOLLER
Qweak
screening
anti-screening
SM
current
proposedCzarnecki and Marciano (2000)Erler and Ramsey-Musolf (2004)
K. Kumar The MOLLER Project at Jefferson Laboratory
Fundamental Symmetries and the Long Range Plan
• We recommend a targeted program of experiments to investigate neutrino properties and fundamental symmetries. These experiments aim to discover the nature of the neutrino, yet unseen violations of time-reversal symmetry, and other key ingredients of the new standard model of fundamental interactions. Construction of a Deep Underground Science and Engineering Laboratory is vital to US leadership in core aspects of this initiative
Experimentalists and theorists pursuing neutrino physics, particle EDMs, double-beta decay, weak decays, and parity-violating electron scattering
collaborated to articulate a grand theme: searches for clues to the early universe that are complementary to the highest energy colliders
while making new discoveries about atoms, nuclei & nucleons
The proposed physics program led to the 3rd recommendation:
The combination of physics potential, technical feasibility, new accelerator capabilities, & a seasoned community have conspired to make MOLLER especially compelling at this time
Ideal training ground for the next generation of scientists for future intiatives in Fundamental Symmetries as well as Hadron Physics
The MOLLER and SOLID experiments are part of the broad initiative above:
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K. Kumar The MOLLER Project at Jefferson Laboratory
Specific LRP Excerpts
These recommendations were the result of:•Endorsement of the physics goals by the larger NP community•Technical success and physics impact of recent parity-violation experiments
The SLAC E158 result was highlighted as one of the 4 major results from the previous seven years in the area of Fundamental Symmetries
E158 made the first measurement of parity-violation in Møller scattering:We propose to improve the result by a factor of 5 with the 11 GeV JLab beam
Page87What are the unseen forces
that were present at the dawn of the universe but
disappeared from view as the universe evolved?
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K. Kumar The MOLLER Project at Jefferson Laboratory
MOLLER Physics Reach
Measurement of Lepton-Lepton Electroweak Reaction
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K. Kumar The MOLLER Project at Jefferson Laboratory
MOLLER Goal
APV = 35.6 ppb δ(APV) = 0.73 ppb δ(QeW) = ± 2.1 (stat.) ± 1.0 (syst.) %
75 μA
δ(sin2θW) = ± 0.00026 (stat.) ± 0.00012 (syst.)
48 weeks
€
δ(sin2ϑW )sin2ϑW
≅ 0.05δ(APV )APV
LH25-17 mrad
11 GeV Beam80% longitudinal polarization
APV !meElabQeW ! (1" 4 sin2 !W)
Precision Measurement of the Electron Weak Charge using Electron-Electron (Møller) Scattering
!!|g2
RR ! g2LL|
= 7.5 TeVLe1e2 =!
i,j=L,R
g2ij
2!2ei!µeiej!
µej
best contact interaction reach for leptons at low OR high energy
To do better for a 4-lepton contact interaction would require: Z factory, linear collider, neutrino factory or muon collider
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K. Kumar The MOLLER Project at Jefferson Laboratory
MOLLER Goal
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0.001 0.01 0.1 1 10 100 1000µ [GeV]
0.23
0.234
0.238
0.242
0.246
sin
2!
W(µ
)
QW
(APV)Q
W(e)
"-DIS
LEP 1
SLC
Tevatron
e-DIS
MOLLER
Qweak
screening
anti-screening
SM
current
proposed
K. Kumar The MOLLER Project at Jefferson Laboratory
New Physics Example
Does Supersymmetry provide a candidate for dark matter?•B and/or L need not be conserved (RPV): neutralino decay•neutralino then unlikely to be a dark matter candidate•neutrinos are Majorana
MSSM sensitivity if light super-partners, large tanβ
PR = (!1)3(B!L)+2s
RPV SUSY
MSSM
MOLLER
Ramsey-Musolf and Su, Phys. Rep. 456 (2008)
SUSY Sensitivity
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Qw
eak
Such probes become even more important if LHC sees an anomaly consistent with SUSY
K. Kumar The MOLLER Project at Jefferson Laboratory
Experimental Design
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K. Kumar The MOLLER Project at Jefferson Laboratory
MOLLER Apparatus28 m
DetectorAssembly
Target
Chamber
Hybrid
First
Toroid
Toroid
“Pots” for insertabletracking detectors
Polarized Beam• Unprecedented polarized luminosity
• unprecedented beam stability
Liquid Hydrogen Target• 5 kW dissipated power (2 X Qweak)
• computational fluid dynamics
Toroidal Spectrometer• Novel 7 “hybrid coil” design
• warm magnets, aggressive cooling
Integrating Detectors• build on Qweak and PREX
• intricate support & shielding
• radiation hardness and low noisecompact structure: plan to make
apparatus and sheilding easily removable17
K. Kumar The MOLLER Project at Jefferson Laboratory
Statistics & Systematicsparameter MOLLER E158 Qweak
Rate 135 GHz 3 GHz 6 GHz
pair stat. width 82.9 ppm 200 ppm 400 ppm
δ(Araw) 0.544 ppb 11 ppb 4 ppb
δ(Astat)/A 2.1% 10% 3%
δ(sin2θW)stat 0.00026 0.001 0.0007
• Elastic e-p scattering– well-understood and testable with data– 8% dilution, 7.5±0.4% correction
• Inelastic e-p scattering– sub-1% dilution– large EW coupling, 4±0.4% correction– variation of APV with r and φ
Irreducible Backgrounds:source of error % errorabsolute value of Q2 0.5beam second order 0.4
longitudinal beam polarization 0.4inelastic e-p scattering 0.4elastic e-p scattering 0.3
beam first order 0.3pions and muons 0.3
transverse polarization 0.2photons and neutrons 0.1
Total 1.018
Accuracy goals are factors of 2 to 10 beyond those of
E158 & Qweak
K. Kumar The MOLLER Project at Jefferson Laboratory
Technical Challenges• ~ 150 GHz scattered electron rate
– Design to flip Pockels cell ~ 2 kHz– 80 ppm pulse-to-pulse statistical fluctuations
• Electronic noise and density fluctuations < 10-5
• Pulse-to-pulse beam jitter ~ 10s of microns at 1 kHz• Pulse-to-pulse beam monitoring resolution ~ 10 ppm and few microns at 1 kHz
• 1 nm control of beam centroid on target– Modest improvementin polarized source laser controls– Improved methods of “slow helicity reversal”
• > 10 gm/cm2 target needed– 1.5 m Liquid Hydrogen target: ~ 5 kW @ 85 μA
• Full Azimuthal acceptance with θlab ~ 5 mrad– novel two-toroid spectrometer– radiation hard, highly segmented integrating detectors
• Robust and Redundant 0.4% beam polarimetry– Plan to pursue both Compton and Atomic Hydrogen techniques
•Currently, design and R&D being done with students and postdocs part-time•One dedicated postdoc focused on spectrometer (thanks!)•Engineering advice is “pro-bono” right now
Collaboration is preparing a
prioritized R&D plan, but the
spectrometer is at the top of the list
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K. Kumar The MOLLER Project at Jefferson Laboratory!"""#$%
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Spectrometer Concept
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K. Kumar The MOLLER Project at Jefferson Laboratoryr (m)
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K. Kumar The MOLLER Project at Jefferson Laboratory
Detector Systems• Integrating Detectors:
– Moller and e-p Electrons:• radial and azimuthal segmentation• quartz with air lightguides & PMTs
– pions and muons:• quartz sandwich behind shielding
– luminosity monitors• beam & target density fluctuationsneutrals
‘pion’
luminosity
• Auxiliary Detectors– Tracking detectors
• 3 planes of GEMs/Straws• Critical for systematics/
calibration/debugging
– Integrating Scanners• quick checks on stability
Moller Peak Detectors
ee’s
ep’s
CAD design in progress
optimized for robust background subtraction
Collaboration physicists will continue to define and optimize
the full suite of detectors 21
K. Kumar The MOLLER Project at Jefferson Laboratory
Status and Outlook
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K. Kumar The MOLLER Project at Jefferson Laboratory
– Polarimetry
– Electronics/DAQ
– Simulations
G. CatesM. Pitt
K. Kumar
M. Gericke and D. MackD. Armstrong
K. PaschkeR. Michaels
D. McNulty
• Steering Committee:– D.Armstrong, R.Carlini, G.Cates, K.de Jager, Y.Kolomensky, K.Kumar (chair),
F.Maas, D.Mack, K.Paschke, M.Pitt, G.Smith, P.Souder, W.van Oers, J. Gomez
• Working Groups & Conveners– Polarized Source– Beam & Beam Instrumentation– Target– Spectrometer– Integrating Detectors– Tracking Detectors
J-P Chen & G. Smith
Recent Evolution•Project received PAC approval: Jan ’09•Director’s review of physics goals and concept: Jan ’10•Collaboration planning targets installation late 2015•Ranking and beamtime in PAC37: Jan ’11 (3 run periods requested)
sub-system Institutionspolarized source UVa, JLab, Miss. St.
Target JLab, VPI, Miss. St.
Spectrometer Canada, ANL, MIT, UVa
Integrating Detectors
Syracuse, Canada, JLab, FIU, UNC A&T, VPI
Luminosity Monitors VPI, Ohio U.
Pion Detectors UMass/Smith, LATech
Tracking Detectors William & Mary, Canada, INFN Roma
Electronics Canada, JLab
Beam Monitoring VPI, UMass, JLab
Polarimetry UVa, Syracuse, JLab, CMU, ANL, Miss. St., Claremont-Ferrand, Mainz
Data Acquisition Ohio U., Rutgers U.
Simulations LATech, UMass/Smith, Berkeley, UVa(Canada: UBC, Manitoba, Winnipeg, TRIUMF)
expression of interest:not yet formalized
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~ 100 Physicists~ 30 institutions
K. Kumar The MOLLER Project at Jefferson Laboratory
– Polarimetry
– Electronics/DAQ
– Simulations
G. CatesM. Pitt
K. Kumar
M. Gericke and D. MackD. Armstrong
K. PaschkeR. Michaels
D. McNulty
• Steering Committee:– D.Armstrong, R.Carlini, G.Cates, K.de Jager, Y.Kolomensky, K.Kumar (chair),
F.Maas, D.Mack, K.Paschke, M.Pitt, G.Smith, P.Souder, W.van Oers, J. Gomez
• Working Groups & Conveners– Polarized Source– Beam & Beam Instrumentation– Target– Spectrometer– Integrating Detectors– Tracking Detectors
J-P Chen & G. Smith
Recent Evolution•Project received PAC approval: Jan ’09•Director’s review of physics goals and concept: Jan ’10•Collaboration planning targets installation late 2015•Ranking and beamtime in PAC37: Jan ’11 (3 run periods requested)
sub-system Institutionspolarized source UVa, JLab, Miss. St.
Target JLab, VPI, Miss. St.
Spectrometer Canada, ANL, MIT, UVa
Integrating Detectors
Syracuse, Canada, JLab, FIU, UNC A&T, VPI
Luminosity Monitors VPI, Ohio U.
Pion Detectors UMass/Smith, LATech
Tracking Detectors William & Mary, Canada, INFN Roma
Electronics Canada, JLab
Beam Monitoring VPI, UMass, JLab
Polarimetry UVa, Syracuse, JLab, CMU, ANL, Miss. St., Claremont-Ferrand, Mainz
Data Acquisition Ohio U., Rutgers U.
Simulations LATech, UMass/Smith, Berkeley, UVa(Canada: UBC, Manitoba, Winnipeg, TRIUMF)
expression of interest:not yet formalized
Two categories of design and R&D
National lab driven: target, spectrometer, beam instrumentationUser driven: source control, detectors, polarimetry
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~ 100 Physicists~ 30 institutions
K. Kumar The MOLLER Project at Jefferson Laboratory
Director’s Review
• Primary Recommendation:– “The Review Committee unanimously recommends that the Director
undertake planning for MOLLER now, to be ready for the 12 GeV Upgrade era.”
• Physics Motivation:– “MOLLER, by exploiting the best qualities of the JLab beam, brings
new information to bear on, and to constrain interpretations of, any new physics that may result at the LHC and elsewhere.”
• Technical Feasibility:– “The Committee could find no technical reasons the goals of MOLLER
could not be reached.”
Doug Beck (Illinois), Dave Hertzog (Illinois), Bob Kephart (Fermilab), Bill Marciano (BNL), Matt Poelker (JLab), Charles Prescott (SLAC, Chair), Michael Schmitt (Northwestern), Glenn Young (JLab), John Weisend (SLAC)
Jan 14-15, 2010: 1.5 days of talks, Homework, Q&A
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K. Kumar The MOLLER Project at Jefferson Laboratory
Director’s Review
• Primary Recommendation:– “The Review Committee unanimously recommends that the Director
undertake planning for MOLLER now, to be ready for the 12 GeV Upgrade era.”
• Physics Motivation:– “MOLLER, by exploiting the best qualities of the JLab beam, brings
new information to bear on, and to constrain interpretations of, any new physics that may result at the LHC and elsewhere.”
• Technical Feasibility:– “The Committee could find no technical reasons the goals of MOLLER
could not be reached.”
Doug Beck (Illinois), Dave Hertzog (Illinois), Bob Kephart (Fermilab), Bill Marciano (BNL), Matt Poelker (JLab), Charles Prescott (SLAC, Chair), Michael Schmitt (Northwestern), Glenn Young (JLab), John Weisend (SLAC)
Jan 14-15, 2010: 1.5 days of talks, Homework, Q&A
A number of detailed recommendations:
First and foremost, bring engineering to bear on the spectrometer design NOW
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K. Kumar The MOLLER Project at Jefferson Laboratory
Spectrometer Engineering• Magnet Advisory Committee formed
– George Clark (TRIUMF), Ernie Ihloff (MIT-Bates), Vladimir Kashikhin (Fermilab), Jim Kelsey (MIT-Bates), Dieter Walz (SLAC) & Robin Wines (JLab)
We face the usual “chicken and egg” story: No funding yet, but need engineering before we fine-tune optics, define footprint, estimate cost and risk
Optics Optimization and Engineering Feasibility
Proposal field map achieved with buildable coil configuration
One dedicated postdoc under my supervision with occasional free engineering advice
The hybrid toroid is the heart of the apparatus
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K. Kumar The MOLLER Project at Jefferson Laboratory
Spectrometer Engineering• Magnet Advisory Committee formed
– George Clark (TRIUMF), Ernie Ihloff (MIT-Bates), Vladimir Kashikhin (Fermilab), Jim Kelsey (MIT-Bates), Dieter Walz (SLAC) & Robin Wines (JLab)
We face the usual “chicken and egg” story: No funding yet, but need engineering before we fine-tune optics, define footprint, estimate cost and risk
Optics Optimization and Engineering Feasibility
Proposal field map achieved with buildable coil configuration
One dedicated postdoc under my supervision with occasional free engineering advice
The hybrid toroid is the heart of the apparatus
Could use real engineering effort by Summer 2011
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K. Kumar The MOLLER Project at Jefferson Laboratory
MOLLER Project
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A small volume apparatus• heavy on engineering design• careful attention must be paid to tolerances• conventional technologies pushed to limits
★ build on previous experience wherever possible
Cost and scheduling exercise begun• aim for a 3 year construction project• availability of technical manpower an issue
A zeroth-order subsystem cost estimate• Currently being checked for completeness• escalated (AY ‘13-’15) ~ 15M$ + contingency
K. Kumar The MOLLER Project at Jefferson Laboratory
Summary and Outlook• Projected Result from an APV measurement in Møller Scattering
• Opportunity with high visibility and large potential payoff– The weak mixing angle is a fundamental parameter of EW physics– A cost-effective project has been elusive until now
• expensive ideas reach perhaps 0.2% (reactor or accelerator ν’s, LHC Z production...)• sub-0.1% requires a new machine (e.g. Z- or ν-factory, linear collider....)
– physics impact on nuclear physics, particle physics and cosmology• pin down parameter for other precision low energy measurements• decipher potential LHC anomalies at the TeV scale• shed light on feasibility of SUSY dark matter via search for R-Parity violation
• NSAC Long Range Plan strongly endorsed the physics– part of fundamental symmetries initiative to tune of 25M$– beginning to attract foreign participation
• 11 GeV JLab beam is a unique instrument that makes this feasible• A motivated collaboration with plenty of experience• Sustains/expands/trains community: feed future nuclear physics needs
δ(sin2θW) = ± 0.00026 (stat.) ± 0.00012 (syst.)
APV = 35.6 ppb δ(APV) = 0.73 ppb δ(QeW) = ± 2.1 (stat.) ± 1.0 (syst.) %
~ 0.1%
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