A. Gasparian NC A&T State University, Greensboro, NC Search for Hidden Sector Scalar Boson in X→γγ Channel with Tagged Photon Beam in Hall B A. Gasparian NC A&T State University, Greensboro, NC Outline physics motivation experiment with current 6 GeV photon tagger proposed tagger upgrade to 11.5 GeV experiment with 11.5 GeV beam summary
Physics Motivation Hidden-Sector searches at Jlab: LIPPS – spin zero particles below e+e- threshold APEX , HPS, DarkLight: vector particles (A’) via e+e- (or μ+μ-) decay This proposal: spin zero particles via γγ-decays with masses complimentary to A’ searches. A. Gasparian Jlab Workshop, March 16, 2012
Physics Motivation: Search for Hidden-Sector Pseudo(Scalars) Spin-zero particles usually arise in field theories from spontaneous U(1) symmetry breaking Scalar bosons (Jp=0+) Higgs’, milli-Higgs [Pospelov&Ritz] Light inflaton mass ~90 MeV [Bezrukov et al., JHEP 1005:010,2010] Dilatons (from string compactification) Pseudo-scalar bosons (Jp=0-) Axions and axion-like particles (solving strong CP-problem) Neutral pion “impostor” [McKeen & Pospelov, [arXiv 1112:2207] (new- particle scenario for pion-photon transition form factor from BaBar) Phenomenology of pseudo Nambu-Goldstone bosons [Frigerio et et al, Phys.Rev. X1 (2011) 021026] (masses ~ MeV) Recent experimental claim for new scalar boson E(38): Interquark exchange of a boson with a mass of about 38 MeV and decaying into 2γ [Beveren & Rupp arXiv:1202.1739v2] A. Gasparian Jlab Workshop, March 16, 2012
Physics Motivation Neutral Pion “Impostor” Introduced new pseudo-scalar or scalar neutral particles with masses close to π0 ‘ coupling to leptons to explain the BaBar experimental result. predicts a 1.8% change in π0 lifetime it is within uncertainty of PrimEx current 2.8% result. A. Gasparian Jlab Workshop, March 16, 2012
Physics Motivation Phenomenology of Pseudo Nambu-Goldstone Bosons A. Gasparian Jlab Workshop, March 16, 2012
Physics Motivation Phenomenology of Pseudo Nambu-Goldstone Bosons More detail questions to A. Afanasev A. Gasparian Jlab Workshop, March 16, 2012
Physics Motivation Inter-quark Exchange of a New Scalar Boson A. Gasparian Jlab Workshop, March 16, 2012
Physics Motivation Inter-quark Exchange of a New Scalar Boson However, these results are unpublished (arXiv:1202.1739v2) A. Gasparian Jlab Workshop, March 16, 2012
Production Mechanism Production Mechanism and Detection: Primakoff-type production To be identified by 2γ decay mode A. Gasparian Jlab Workshop, March 16, 2012
Search Experiment with 6 GeV Tagger in Hall B We propose to search for X- scalar bosons in: electro-production on heavy nuclei (virtual photon tagging): e- + Au → e’ + γ* + Au → e’ + X + Au X → γγ with Hall B photon Tagging facility tagger magnet for cleaning the charged background also PS dipole magnet as second cleaning magnet PbWO4 crystal calorimeter (upgraded to 1x1 m2 ) for better Mγγ resolution Tagger radiator PS Dipole HyCal Tagger magnet Beam dump A. Gasparian Jlab Workshop, March 16, 2012
Schematic View of the Proposed Experiment with 6 GeV Tagger γ 6 GeV e- beam γ-beam γ A. Gasparian Jlab Workshop, March 16, 2012
Characteristics of the Proposed Experiment (6 GeV Beam) MX = 20 MeV σ = 0.43 MeV Elasticity σ = 81 MeV A. Gasparian Jlab Workshop, March 16, 2012
Limits of the Proposed Experiment with Current Tagger tagger exit pipe limit A. Gasparian Jlab Workshop, March 16, 2012
Design Concepts of the Proposed Experiment with 11.5 GeV Beam Design assumptions for upgrading tagger to 11.5 GeV: No change in tagger magnet No change in exit pipe No change in tagger beam dump operational at 6 GeV Proposed #1 version add new short and high B superconducting dipole before existing Tagger: Does not work New Dipole PS Dipole 11.5 GeV e- beam HyCal Tagger magnet Beam dump Tagger field map from D. Sober A. Gasparian Jlab Workshop, March 16, 2012
Two Magnet Solution for 11.5 GeV Tagger We suggest to add two identical superconducting magnets : length 1.0 m integral BdL 5.5 Tm New Dipole #1 PS Dipole 11.5 GeV e- beam HyCal New Dipole #2 Tagger magnet initial bend angle: θ = 6.50 entrance height change: -7.5 cm exit height change: -4.5 cm Beam dump Tagger field map from D. Sober A. Gasparian Jlab Workshop, March 16, 2012
Invariant Mass Range with 11.5 GeV Beam MX = 80 MeV σ = 0.83 MeV A. Gasparian Jlab Workshop, March 16, 2012
Combined Invariant Mass Range A. Gasparian Jlab Workshop, March 16, 2012
X 400 pb for MX = 50 MeV Estimated Count Rates Based on model predictions we estimated to be: X 400 pb for MX = 50 MeV A. Gasparian Jlab Workshop, March 16, 2012
Anticipated Sensitivity vs Beam Dump Experiments Beam dump constraints compiled in Andreas et al, arXiv 1005.3978 Estimated region of parameter space to be probed in the proposed measurement
Summary A search experiment is proposed for hidden sector scalar bosons with Hall B tagger in neutral channel decays: X upgraded Hall B photon tagging facility to 11.5 GeV beam upgraded PbWO4 crystal calorimeter to 1x1 m2 total size Upgraded tagger will be a good addition to Hall B physics program with CLAS12 Advantages of the proposed experiment: large acceptance range for Mx (5 – 120) MeV high resolution in invariant mass (0.84 MeV @ MX = 80 MeV) high detection efficiencies (~20%) relatively low experimental background (charged) Work in progress for evaluation of sensitivity limits in X-boson parameter space and optimization of experiment (including background studies) Enrich Jlab Program in Physics Beyond Standard Model A. Gasparian Jlab Workshop, March 16, 2012