Search for a leptophobic B-boson via η decay at Jlab Liping Gan University of North Carolina Wilmington Outline Motivation to search for a leptophobic B-boson in decay. Jlab Eta Factory (JEF) experiment with GlueX Projected JEF experimental reach Status of GlueX Summary
“Vector Portal” to Dark Sector Dark photon A’ Dark leptophobic B-boson (dark ω, γB , or Z’): Kinetic mixing and U(1)’ Gauged baryon symmetry U(1)B T.D. Lee and C.N. Yang, Phys.Rev.,98, 1501 (1955) the stability of baryonic and dark matter a unified genesis of baryonic and dark matter a natural framework for resolving “Strong CP problem” in QCD M.Graesser, I. Shoemaker and L. Vecchi, arXiv:1107.2666 Most A’ searches look for A’l+l-, relying on the leptonic coupling of new force
Landscape of new GeV-scale forces Dark photon searches (di-lepton resonances) Blind spot for dark photon searches
Experimental probes for B-boson Discovery signals depend on the B mass: the region is strongly constrained by long-range forces search and nuclear scattering experiments. the region has been investigated by the collider experiments. GeV-scale domain is nearly untouched. a discovery opportunity hiding in nonperturbative QCD regime!
How to search for dark bosons?
Striking signature for B-boson in 0 B production: A.E. Nelson, N. Tetradis, Phys. Lett., B221, 80 (1989) B decays: highly suppressed SM background B0 in 140-620 MeV mass range B+0 Search for a resonance peak of 0 for mB ~140-550 MeV S. Tulin, Phys.Rev., D89, 14008 (2014)
Jlab Eta Factory (JEF) experiment FCAL Simultaneously measure η decays: η→0, η→3, and … η produced on LH2 target with 9-11.7 GeV tagged photon beam: γ+p → η+p Reduce non-coplanar backgrounds by detecting recoil p’s with GlueX detector (75%) Upgraded Forward Calorimeter with High resolution, high granularity PbWO4 insertion (FCAL-II) to detect multi-photons from rare η decays 7
Overview of the JEF project Main physics goals: Search for a leptophobic dark boson (B). Directly constrain CVPC new physics Probe interplay of VMD & scalar resonances in ChPT to calculate O(p6) LEC’s in the chiral Lagrangian. Determine the light quark mass ratio FCAL-II is required for the rare decays
World competition in η decays e+e- Collider Low energy -facilities High energy -facility hadroproduction Fixed-target CBELSA/TAPS at ELSA JEF at Jlab photoproduction
Filter Background with η Energy Boost (0) A2 at MAMI (Phys.Rev. C90 (2014) 025206): p→ηp (Eγ=1.5 GeV) p→ 00 + p η →000 Jlab: p→ηp (E = 9-11.7 GeV)
New Equipment: FCAL-II PrimEx HyCal FCAL with PWO insertion: 118x118 cm2 in Size (3445 PbWO4) 2cm x 2cm x 18cm per module HyCal S/N Ratio vs. Calorimeter Types signal: , background: FCAL (Pb glass) FCAL-II (PbWO4) vs. FCAL (Pb glass) S/N=0.1 Property Improvement factor Energy σ 2 Position σ Granularity 4 Radiation-resistance 10 FCAL-II (PbWO4) S/N=10
Hadronic Backgrounds Reduction in 4 States Event Selection Elasticity is EL=ΣE/ Etagged- Energy conservation for γ+p → η+p reaction: ΔE=E()+E(p)-E(beam)-M(p) Co-planarity Δ= ()- (p) Note: Statistics is normalized to 1 beam day. BG will be further reduced by requiring that only one pair of ’s have the 0 invariant mass. Signal: 0
Reconstructed B Mass Resolution mB=200 MeV mB=350 MeV mB=500 MeV The upper-left picture shows the GlueX detector just prior to the start of data taking in October 2014. The upper-right picture shows the omega(782) decaying into three pions. The reactions gamma p to pi+ pi- pi0 is reconstructed, and then kinematically fit to a missing proton. The pi0 is reconstructed through Its two photon decay, where both photons are seen in the forward calorimeter. The beam photon is tagged and Only photons in the energy range of 7GeV to the end-point of the beam are selected. The lower-left picture shows events where a positive and negative particle are reconstructed as originating from a vertex more than 5cm from the CH2 plastic target. Under the assumption that both particles are pions, the plot shows The invariant mass of the two pions. A clear signal for the KS is seen. The lower-right picture shows the start counter mounted on the liquid hydrogen target just prior to insertion into the GlueX detector.
JEF Experimental Reach (B0 ) A stringent constraint on the leptophobic B-boson in 140-550 MeV range. A positive signal of B in JEF will imply a new fermion with a mass up to a few TeV due to electro-weak anomaly cancellation. Future ’ experiment will extend the experimental reach up to 1 GeV 100 days of beam time Constraints from A’ search (KLOE and WASA) assumed:
Enhanced capabilities Jlab and GlueX New Hall Add arc Enhanced capabilities in existing Halls Add 5 cryomodules 20 cryomodules Upgrade arc magnets and supplies CHL upgrade The upper-left picture shows the GlueX detector just prior to the start of data taking in October 2014. The upper-right picture shows the omega(782) decaying into three pions. The reactions gamma p to pi+ pi- pi0 is reconstructed, and then kinematically fit to a missing proton. The pi0 is reconstructed through Its two photon decay, where both photons are seen in the forward calorimeter. The beam photon is tagged and Only photons in the energy range of 7GeV to the end-point of the beam are selected. The lower-left picture shows events where a positive and negative particle are reconstructed as originating from a vertex more than 5cm from the CH2 plastic target. Under the assumption that both particles are pions, the plot shows The invariant mass of the two pions. A clear signal for the KS is seen. The lower-right picture shows the start counter mounted on the liquid hydrogen target just prior to insertion into the GlueX detector.
Status of GlueX The upper-left picture shows the GlueX detector just prior to the start of data taking in October 2014. The upper-right picture shows the omega(782) decaying into three pions. The reactions gamma p to pi+ pi- pi0 is reconstructed, and then kinematically fit to a missing proton. The pi0 is reconstructed through Its two photon decay, where both photons are seen in the forward calorimeter. The beam photon is tagged and Only photons in the energy range of 7GeV to the end-point of the beam are selected. The lower-left picture shows events where a positive and negative particle are reconstructed as originating from a vertex more than 5cm from the CH2 plastic target. Under the assumption that both particles are pions, the plot shows The invariant mass of the two pions. A clear signal for the KS is seen. The lower-right picture shows the start counter mounted on the liquid hydrogen target just prior to insertion into the GlueX detector.
Commissioning: Fall 2014 and Spring 2015
“Physics” Data
Summary 12 GeV tagged photon beam with GlueX setup offers a unique opportunity for discovering weakly-coupled new forces in neutral mode. It provides two orders of magnitude in background reduction in the neutral rare decays compared to other facilities in the world. The JEF experiment will probe a leptophobic dark B-boson in 140-550 MeV range via B0 (complementary to ongoing A’ search), with sensitivity to the baryonic fine structure constant αB as low as 10−7. Future ’ experiment will extend the experimental reach for the B mass up to 1 GeV
Production Rate Estimation LH2 target length L=30cm, =0.0708 g/cm3 The +p→η/η’+p cross section: ~70 nb for η; ~57 nb for η’ J.M. Laget , Phys.Rev. , C72, 022202 (2005) and A. Sibirtsev et al. Eur.Phys.J., A44, 169 (2010) Photon beam intensity Nγ~5x107 Hz (for Eγ~9-11.7 GeV) Jlab Eta Factory (JEF) (η’/day)