Update on JEF project Update on JEF project Liping Gan (On behalf of JEF working group)  Where we are now?  Outcome from the eta physics workshop at ACFI  Plan for PAC42 and beyond Outline Outline 1

Proposal to PAC40 in 2013 Perform a simultaneous measurement of η decays to all neutral final states:  η →  0 , measure BR (~4% precision) and Dalitz distribution to determine two O(p 6 ) LEC’s in the chiral Lagrangian.  Improve BR upper limits by 1-2 orders of magnitude for SM forbidden decays:  η → 3 , η → 2  0 , and other C-violating neutral channels offer the best window for direct test of C-violating and P-conserving new physics.  A new measurement on η → 3  0 with a significant different systematics to constrain the light quark mass ratio. 2

3 Projected JEF Results Proj. JEF BR Upper Limit

Jlab PAC40 report on the JEF proposal  Feasibility: “The proposed measurements appear to be feasible and the experiment is well suited for the tagged Hall D photon beam.” “The proposed measurements appear to be feasible and the experiment is well suited for the tagged Hall D photon beam.”  Issues: “The PAC recognizes the scientific interest of performing new measurements of rare eta decays with improved sensitivity to test the SM. However, the PAC identified some issues, mainly related to the theoretical implications of these measurements.” “The PAC recognizes the scientific interest of performing new measurements of rare eta decays with improved sensitivity to test the SM. However, the PAC identified some issues, mainly related to the theoretical implications of these measurements.” 4

Workshop on “Hadronic Probes of Fundamental Symmetries” March 6-8, 2014, Amherst Center for Fundamental Interactions, University of Massachusetts Amherst Web site: probes-of-fundamental-symmetriesParticipants: 5 Gilberto ColangeloGilberto Colangelo John DonoghueJohn Donoghue Barry HolsteinBarry Holstein Gene GolowichGene Golowich Michael R-MMichael R-M Susan GardnerSusan Gardner Basian KubisBasian Kubis Johann BijnensJohann Bijnens Jens ErlerJens Erler Sean TulinSean Tulin Jose GoityJose Goity Students and postdocs from ACFIStudents and postdocs from ACFI Andrzej Kupsc Marc Unverzagt Eugene Chudakov Dave Mack Simon Taylor Liping Gan Rory Miskimen Alexander Somov

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1. What is the physics impact of prospective JEF → π 0 γγ measurement?  Probe interplay of VMD & scalar resonances in ChPT  an unique window to test the role of scalar dynamics  Provide a stringent constraint on the dark B-boson in MeV range. 7

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11 Projected JEF Results Proj. JEF

12 Sean Tulin

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14 Sean Tulin

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2. What is the physics impact of prospective JEF → 3π measurement? → 3π measurement?  More precise value for quark mass ratio ( ): fundamental parameters of SM that can be determined fundamental parameters of SM that can be determined  Have a wide-range impact. Example: improve the extraction of V us from Example: improve the extraction of V us from Improved V us would then lead to improved tests of CKM Improved V us would then lead to improved tests of CKM unitarity: unitarity:  Global context as cross check on systematics  Suggest to consider the charged pion final state as well 20

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Uncertainties in quark mass ratio 24

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26 Emilie Passemar

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3. What are the possible new opportunities for probing physics beyond the Standard Model (BSM) with low- energy hadronic probes?  C violation with P conservation (CVPC) in eta decay BR's could avoid EDM constraints (in a conspiracy scenario which might imply a hidden symmetry)  the theorists are still debating whether effective CVPC ASYMMETRIES in eta decays and neutron decays are constrained by EDMs at all. 30

31 Michael R-M ( ) (M. Ramsey-Musolf et. al., phys. Rev., D63, (2001) )

32 Michael Ramsey-Musolf slide on C violation with P conservation

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35 Physics foci Physics foci test the role of scalars in ChPT and probe  η →  0  : test the role of scalars in ChPT and probe dark B-boson for new physics dark B-boson for new physics  η → 3  0 and η →  0  +  - : constrain the light quark mass ratio (provide an important cross check with significant different systematics on  3  results from European facilities)  C-violating decays (η → 3 , η → 2  0  ) and asymmetry in η →  0  +  - : probe C-violating, P-conserving new physics. 35

Plan for PAC42 and beyond  Get updated proposal ready for June 2 submission to PAC42  Two new theory focus groups (ChPT and BSM) have formed. They will provide new theory sections to address the issues raised by PAC40. (Due date is the first week of May)  The first draft of proposal will be submit to the collaboration on May 12.  Join the European meson physics network  Keep close collaboration with theorists on the project 36

The End Thanks you! 37

World Competition in η Decays 38 JEF at Jlab Low energy  -facilities Low energy  -facilities High energy  -facility CBELSA/TAPS at ELSA e + e - Collider Fixed-target photoproduction hadroproduction

Filter Background with η Energy Boost (  0  ) Filter Background with η Energy Boost (  0  ) 39 Major Background Major Background  η →  0  0  0  6    - p →  0  0 + neutron GAMS Experiment  - p → η p ( E  = 30 GeV )  - p → η p ( E  = 30 GeV ) Jlab:  p → ηp Jlab:  p → ηp (E  = GeV) CB-AGS Experiment  - p → η p (E  =730 MeV)  - p → η p (E  =730 MeV) η →  0  0  0

40 Proposed Experiment in Hall D Simultaneously measure η neutral decays: η →  0 , η → 3 , and … 40  η produced on LH 2 target with GeV tagged photon beam: γ+p → η+p γ+p → η+p by detecting recoil p’s with GlueX detector  Reduce non-coplanar backgrounds by detecting recoil p’s with GlueX detector  Upgraded Forward Calorimeter with High resolution, high granularity PbWO 4 (FCAL-II) to detect multi-photons from the η decays PbWO 4 (FCAL-II) to detect multi-photons from the η decays FCAL

Hadronic Backgrounds Reduction in 4  States 41 Event Selection  Elasticity is EL=ΣE  / E tagged-   Energy conservation γ+p → η+p reaction 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 