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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
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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
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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) ] (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: v2] A. Gasparian Jlab Workshop, March 16, 2012
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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
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Physics Motivation Phenomenology of Pseudo Nambu-Goldstone Bosons
A. Gasparian Jlab Workshop, March 16, 2012
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Physics Motivation Phenomenology of Pseudo Nambu-Goldstone Bosons
More detail questions to A. Afanasev A. Gasparian Jlab Workshop, March 16, 2012
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Physics Motivation Inter-quark Exchange of a New Scalar Boson
A. Gasparian Jlab Workshop, March 16, 2012
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Physics Motivation Inter-quark Exchange of a New Scalar Boson
However, these results are unpublished (arXiv: v2) A. Gasparian Jlab Workshop, March 16, 2012
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Production Mechanism Production Mechanism and Detection:
Primakoff-type production To be identified by 2γ decay mode A. Gasparian Jlab Workshop, March 16, 2012
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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
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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
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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
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Limits of the Proposed Experiment with Current Tagger
tagger exit pipe limit A. Gasparian Jlab Workshop, March 16, 2012
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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
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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
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Invariant Mass Range with 11.5 GeV Beam
MX = 80 MeV σ = 0.83 MeV A. Gasparian Jlab Workshop, March 16, 2012
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Combined Invariant Mass Range
A. Gasparian Jlab Workshop, March 16, 2012
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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
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Anticipated Sensitivity vs Beam Dump Experiments
Beam dump constraints compiled in Andreas et al, arXiv Estimated region of parameter space to be probed in the proposed measurement
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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 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
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