Aspects of The Standard Model and Beyond

Transcription

1 Aspects of The Standard Model and Beyond Hadronic Physics Town Meeting at DNP2012 October 25, 2012 Mark Pitt Virginia Tech Parity violating electron scattering at JLab Proton s weak charge: Qweak Electron s weak charge: MOLLER Heavy photon searches at JLab APEX, Heavy Photon Search, DarkLight

2 Neutral Currents Beyond the Standard Model Many new physics models require new, heavy, neutral current interactions Heavy Z s and neutrinos, technicolor, compositeness, extra dimensions, SUSY Low energy WNC interactions (Q 2 <<M Z2 ) Z 0 Consider f 1 f 1 f 2 f 2 or f 1 f 2 f 1 f 2 Eichten, Lane and Peskin, PRL50 (1983) mass scale, coupling g for each fermion and handedness combination Sensitivity to TeV scale contact interactions if: δ(sin 2 θw) 0.5% away from the Z resonance Precision neutrino scattering PV couplings through interference with EM opposite parity transitions in heavy atoms parity violating electron scattering 2

3 Parity Violation in Electron Scattering Weak Charge QW unpolarized target (g Ae g VT + g Ve g AT ) Electromagnetic amplitude interferes with Z-exchange as well as any new physics Current/future Jlab PVES program significant improvement on precision of couplings e C 2g ee e V e g e A Qweak (data taken, analyzing) Mainz MESA P2 (proposed) PV-DIS-6 (completed) SOLID (JLab 12 GeV) SLAC E158 (completed) MOLLER (JLab 12 GeV) 3

4 Qweak: Proton Weak Charge e + p elastic at JLAB Data taking done ( ) After full analysis expect: Q W p 4% (sin 2 W ) 0.3% Technical highlights: World s highest power cryotarget (2.3 kw) (< 40 ppm boiling at 180 A) 180 A, 86% polarized beam Compton and Moller polarimetry Low noise, high precision electronics First result! Session DA2; ~ 4% of data p Q W Future: MESA/P2 at Mainz New ERL complex will also support a highcurrent extracted beam suitable for a PV measurement of proton weak charge APV = 20 ppb to 2.1% (0.4ppb) δ(sin 2 θw) = 0.2% Funding approved from DFG Development starting now Planned running

5 MOLLER at 11GeV JLab An ultra-precise measurement of the weak mixing angle using Møller scattering 1 e APV E lab QW, Figure of Merit proportional to beam power E lab At 11 GeV, JLab luminosity and stability makes large improvement possible MOLLER APV = 35.6 ppb Luminosity: 3x1039 cm2/s 75 μa 80% polarized δ(apv) = 0.73 parts per billion δ(qew) = ± 2.1 % (stat.) ± 1.0 % (syst.) δ(sin2θw) = ± (stat.) ± (syst.) ~ 0.1% Matches best collider (Z pole) measurement! Mark Pitt JLab PVES/Dark Photon Hadronic Town Meeting, DNP, Oct

6 Precision Measurement of sin 2 θw Direct measurement of SM weak mixing angle is average of two measurements that disagree by 3σ......yet the naive statistical average agrees to a very high level with the LHC Higgs candidate We failed to nail sin 2 θw when we had the colliders! B.Marciano The consistency of the SM prediction, between directly measured mh, mw, mt, sin 2 θw bears testing sin 2 θ W improvements at hadron colliders very challenging Giga Z option of ILC or neutrino factory: powerful but far future 6

7 MOLLER Sensitivity to BSM Physics best contact interaction reach for leptons at low OR high energy To do better for a 4-lepton contact interaction would require: Giga-Z factory, linear collider, neutrino factory or muon collider Heavy Photons: The Dark Sector Z d MOLLER reach: red dashed lines Beyond kinetic mixing: introduce mass mixing with Z Davoudiasl, Lee, Marciano arxiv: v2 Leads to new source of low energy parity violation ( dark parity violation ) Complementary to direct heavy photon searches: Lifetime/branching ratio model dependence vs mass mixing assumption 7

8 Meeting the Challenges of MOLLER Technical goals: sub part per billion (ppb) statistical reach and systematic control sub 1% normalization control Unprecedented Precision ~ 150 GHz scattered electron rate (80ppm at 2kHz) 100% Azimuthal acceptance, with θ lab ~ 5 15 mrad Robust and redundant 0.4% beam polarimetry 1 nm control of beam centroid on target > 10 gm/cm 2 target needed, 5kW power Preparations on Track ee s ep s Strong Collaboration being formed with international participation JLab Director s Review (chair: C. Prescott) gave strong endorsement Conceptual design and cost range being developed (~ 20M$) Funding proposal has been submitted to DoE ~3 years construction, aim to complete data collection in

9 Dark Heavy Photons Interesting range to explore: ~ ' and m(a ) ~ MeV GeV One of the very few portals for a new force to communicate with the Standard Model Coupling of new neutral vector boson A ( dark heavy photon ) to charged matter given by q = e Can explain g 2 discrepancy Can explain positron excess in satellite data Search Strategy for JLab Experiments A Signal QED backgrounds: radiative Bethe Heitler Strategy: Search for e + e resonance associated with A in continuum QED background Bjorken, Essig, Schuster, Toro, Phys. Rev. D80 (2009)

10 Dark Heavy Photons JLab Program Test runs in 6 GeV era, full runs in 12 GeV era APEX in Hall A The A Experiment Tungsten target + existing high resolution spectrometers Recently published test run results PRL 107 (2011) black: data red: MC of QED bckg blue: e+e accidentals Heavy Photon Search in Hall B Dedicated detector downstream of CLAS12 Forward vertexing spectrometer; can measure displaced vertex Parasitic test run compete in 2012 HEP funded DarkLight Detecting a Resonance Kinematically with Electrons Incident on a Gaseous Hydrogen Target JLab FEL (~ 1 ma, 100 MeV) on H2 gas jet target Full final state reconstruction Successful Test Run (July 2012) Seeking funding 2 10

11 Summary: Compelling new opportunities in PVES and Dark Photon Searches PVES: Since 2007: New constraint on quark vector weak charges (Completion of Strange quark program) (First electroweak observation of neutron skin in a heavy nucleus) Successfully completed PV DIS 6 running (recent results) Successfully completed QWeak running (first results out) MOLLER at JLab Ultra precise weak mixing angle comparable to the best collider measurements, needed and unavailable anywhere else! TeV scale BSM sensitivity to complement LHC P2 at Mainz Factor of two and low Q 2 available on Qw p Extend precision and improved interpretation Dark Photon Searches New opportunity since 2007; JLab s capabilities well tailored to it Three experiments planned: APEX, Heavy Photon Search, DarkLight Complementary approaches map out different regions in the mass coupling parameter space Thanks to Kent Paschke for many of these slides. 11