Dark Forces search at JLab

INFN-CSNIII Roma, February 5th 2013 Dark Forces search at JLab M.Battaglieri INFN -GE, Italy Physics case (top-down) Experimental evidence (bottom-up) Experiment search overview Dark forces search at JLab 1

http://www.lnf.infn.it/ conference/dark/ 2

How to look for new physics LHC range: mx~1tev, x~ SM First results show no hints of new strongly-interacting states or new heavy EW bosons (other than Higgs) What about if: mx~1gev, x<10-6? Important progress in neutrino physics, dark matter sensitivity, precise frontier measurements Precise experiments at low/moderate energy CSNIII Physics!!! 3

Forces in nature 4 fundamental interactions known so far: strong, electromagnetic, weak and gravitational Are there other interactions? how could we know about? what could be their properties? Particles, interactions and symmetries Known particles & new forcecarriers New particles & new forcecarriers Particles: quarks, leptons Force-carriers: gluons,, W, Z, graviton (?), Higgs,... Dark Matter Spin-1: U bosons ( hidden or dark photons) Spin-0: Axions (or axion-like particles) New bosons are expected to mediate new interactions 4

Neutral doors (Portals) to include DM in the SM There are (many) possible ways to include the DM into the SM Some of them can be tested directly (e.g. rare B-decays) A simple way to go beyond the SM (not yet excluded!): SU(3)C x SU(2)L x U(1)Y x extra U(1) Color Electroweak Hypercharge Hidden sector Hidden sector (HS) present in string theory and super-symmetries HS not charged under SM gauge groups (and v.v.) no direct interaction between HS and SM HS-SM connection via messenger particles Hidden Visible /A couples to SM via electromagnetic current (kinetic mixing) mixing angle = ~ 10-6 -10-2 ( / = 2 ) is a huge mass scale particle (M~1EeV) coupling to both SM and HS 5 /A got mass with a complicated mechanisms (Higgs or Stuckelberg) m ~ e MEW (MZ or TeV) ~ MeV - GeV scale

Consequences /A decays in leptons abundance of e+e- in Universe /A couples to SM via electromagnetic current (kinetic mixing) short range modification of EM interaction /A couples weakly to SM particles long lived states Assumption: no light dark fermions /A decay back to SM particles Prompt decay BF (A hadrons/a leptons) ~ M 2 (A ) Above 1.2 GeV hadronic decays dominate 6

Astrophysical motivation: the 511 kev line Positron and antiproton abundance from PAMELA 511 kev line map from GRAL/SPI data Unexplained concentration of 511 kev line from the galactic center Diffuse emission Increasing fraction of e+/e- measured by PAMELA No surprise with antiprotons (sub GeV mass gauge boson?) It is very difficult to explain PAMELA results with standard DM (WIMPS): needs a boost of 100-1000 Dark forces may explain it by DM decay/annihilation 7

Dark forces and dark matter (heavy WIMP - light mediators) Annihilation - Decay Direct detection Hidden photon with mass m and mixing Additional Dirac fermion fermion with mass m Elastic scattering on nuclei mediated by Comparison with experiments DAMA/LIBRA claims Annihilation of trough and into This is only one of the possible DM model! 8

Modification of EM g-2 of muon g-2 is expected to be 0 Discrepancy >3 Some (complicated) strong interaction dynamic? New physics?

Modification of EM g-2 of muon g-2 is expected to be 0 BaBar Discrepancy >3 Some (complicated) strong interaction dynamic? New physics? Vector (dark) force could account for the discrepancy 10

Modification of EM g-2 of muon g-2 is expected to be 0 BaBar Discrepancy >3 Some (complicated) strong interaction dynamic? New physics? muonic hydrogen Lamb shift Vector (dark) force could account for the discrepancy muon 200 times closer to p (w.r.t. hydrogen) New forces for muon? 11

Particle physics search of A / (hidden photon) Fixed target: e N N N Lepton Lepton+ JLAB, MAINZ Annihilation: e+e- µµ BABAR,BELLE,KLOE Fixed target: p N N p Lepton Lepton+ FERMILAB, SERPUKHOV 12 Meson decays: 0,,,, ( ) Lepton Lepton + ( ) KLOE, BES3, WASA-COSY

Particle physics search of (hidden photon) Fixed target: e N N N Lepton Lepton+ JLAB, MAINZ Fixed target: p N N p Lepton Lepton+ FERMILAB, SERPUKHOV Annihilation: e+e- µµ BABAR,BELLE,KLOE Meson decays: 0,,,, Lepton Lepton+ KLOE, BES3, WASA-COSY Parameter space Coupling vs Mass No positive signal (so far) but limits in parameter space coupling vs mass 13

Fixed target experiments e- beam incident on thick target is produce in a process similar to ordinary Bremsstrahlung carries most of the beam energy emitted forward at small angle decays before the detector Multiple experimental approaches, with different strategies for fighting backgrounds: l d cm: beam dump; low background l d cm: vertex; limited by instrumental bg l d cm: bump hunt; fight bg with high intensity, resolution 14

Beam dump limits KEK Japan (1986) search for axion-like particles 27 mc electrons dumped at 2.5 GeV shield: 3.5 cm tungsten, 2.4 m iron decay volume: 2.2 m Orsay France (1989) search for light Higgs bosons 3.2 mc electrons dumped at 1.6 GeV shield: 65 cm tungsten, 1 m lead decay channel: 2 m SLAC E141 (1987) SLAC E137 (1988) Fermilab E774 (1991) Parameters (at fixed m) L shield max (should be small) L decay min (should be large) Beam energy shift the whole area (larger to higher) Ne min (should be large) 15

Overall limits and JLab experiments DARK LIGHT (FEL) APEX (Hall-A) HPS (Hall-B) Unconventional use of the CEBAF PAC approval (max rating conditioned to technical feasibility) Positive run-tests Experiments begin: 2015-16 JLAB12 involved in HPS New collaborators are welcome! α = 2 α (α = ε2 /4π ) 16

Jefferson Lab and the CEBAF Arc Lin Lin FEL Arc 17 3 End Sta.ons Hall- A, Hall- B, Hall- C

The CEBAF parameters Primary Beam: Electrons Beam Energy: 6 GeV (12 GeV soon) + Free Electron Laser (FEL) 100% Duty Factor (cw) Beam Polarization (beam and reaction products) L > 10 6 x SLAC at the time of the original DIS experiments! JLab12 luminosity will increase by 10 x 12 GeV upgrade Upgrade of the accelerator Construction of new equipment for Hall A, B and C Construction of new experimental Hall (D) 16-month installation: May 2012 Sept 2013 Hall A commissioning start Feb 2014 Hall D commissioning start Oct 2014 Halls B/C commissioning start April 2015 Project Completion June 2015 18

JLab experiments DARK LIGHT Detecting A Resonance Kinematically with electrons Incident on a Gaseous Hydrogen Target High intensity (ma) low energy (100 MeV) electron beam using JLab s FEL on diffuse H2 gas target FEL DM Search Relevant Characteristics e- beam energy: 80 130 MeV e- beam rate: pulsed to CW e- beam current: up to 10 ma Light is linearly polarized Luminosity: 1 ab -1 /month 19

JLab experiments APEX (A-Prime EXperiment) Dark photon search in fixed target experiment in Hall-A at Jefferson Lab Looking for a small, narrow bump on top of a smooth histogram of QED processes Excellent mass resolution required (~ 0.85-1.1MeV) QED trident Very similar to Mainz kinematics BG Peaked at M=0 Simulations for Mainz setup (E=850MeV) 20

JLab experiments APEX (A-Prime EXperiment) Dark photon search in fixed target experiment in Hall-A at Jefferson Lab Looking for a small, narrow bump on top of a smooth histogram of QED processes Excellent mass resolution required (~ 0.85-1.1MeV) QED trident Test run set up 21

JLab experiments APEX APEX full run projected sensitivity e+e- statistics 200x / 2 orders of magnitude below current limits Beam energy from 1.1 GeV to 4.4 GeV Beam current: 60-100 μa Ready to run after resuming operations APEX test run Relevant Characteristics Beam current up to 150μA Target: Ta foil, 22 mg/cm2 HRS Central momenta: 1.13 GeV Momentum acc: ± 4.5% Electron beam energy: 2.26 GeV Solid angle acceptance: ~2.8 msr 22

JLab experiments HPS (Heavy Photon Search) Heavy photon search in fixed target experiment in Hall-B at Jefferson Lab Invariant mass and separated vertex Signal BG: QED trident Bump Hunt εe A BG Decay lenght Requirements: forward angles coverage detector close to the target good spacial resolution: vertex~1mm (vertexing) good mass resolution: A mass~1 MeV (bump hunting) A kinematics E A E beam θ A 0 θ decay = m A /E A 23

JLab experiments HPS, test run Test run in spring 2012 e- beam Dipole Magnet Tracker/Vertexer Electromagnetic Calorimeter - 442 PbWO 4 modules with APD readout in a temperature controlled enclosure, starting @ 15mrad Vacuum chamber between 2 parts of the ECal ECal Si tracker - 5 layers (axial+stereo), microstrip Res: ~6 um ~2-3 ns Target - 0.125% r.l. W-target (4mm) bend plane 24

Adding muon detection capability to exp setup A decay in µ + µ - Reduced em BG (pion decay only) Pion-pair rejection factor < 10-4 1m-long multy-layers of plastic scintillator + Iron absorber JLab experiments HPS HPS could discover True Muonium (µ + µ - ) Long lived bound state (10 kev binding energy) Decay in e+ e- c = 35 mm at 6 GeV Looks like an A but known rate and lifetime TM 25

JLab experiments HPS The full proposal will be presented in spring 2013 Expected beam time in Fall 2014 / Spring 2015 Extended capability adding a muon-detector Bump hunting Bump hunting + vertexing 1 week 1.1 GeV 1 week 2.2 GeV 3 months 2.2 GeV 3 months 6.6 GeV 26

Other searches Nuclear transitions e + e - pairs from magnetic monopole 0-0 + transitions in 16 O using 14 N( 3 He,p) 16 O Rare K decays Long lived exotics at LHCb, ATLAS, CMS, BABAR (M>10GeV) Axions-like low mass particles (M<1MeV) 27

Conclusions 74% 4% 22% Matter Dark Matter Dark Energy It seems established that hadronic matter only accounts for the 4% of the total mass in the Universe Strong physics motivation for the possible existence of GeVscale hidden/dark photons: top-down: extra U(1)s in string models bottom-up: anomalies associated with dark matter (PAMELA, FERMI) and (g 2)μ Fixed-target experiments well suited to attack dark forces JLab is one of the major player in the MeV-GeV mass range search Results will come shortly! 28