Dark Forces search at JLab

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1 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

2 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:

3 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?

4 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

5 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 = ~ ( / = 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

6 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

$emission Increasing fraction of e+/e- measured by PAMELA No surprise with antiprotons (sub GeV mass gauge boson?$

7 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 Dark forces may explain it by DM decay/annihilation 7

fermion with mass m Elastic scattering on nuclei mediated by Comparison with

8 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

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

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? Vector (dark) force could account for the discrepancy 10

11 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

12 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

13 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

14 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

15 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

16 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: JLAB12 involved in HPS New collaborators are welcome! α = 2 α (α = ε2 /4π ) 16

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

18 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

diffuse H2 gas target FEL DM Search Relevant Characteristics e- beam energy: 80 130 MeV e- beam

19 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: 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

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 (~ MeV) QED trident Very similar to Mainz kinematics BG Peaked at M=0 Simulations for Mainz setup (E=850MeV) 20

small, narrow bump on top of a smooth histogram of QED processes

21 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 (~ MeV) QED trident Test run set up 21

4 GeV Beam current: 60-100 μa Ready to run after resuming operations APEX test run Relevant Characteristics

22 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: 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

23 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

442 PbWO 4 modules with APD readout in a temperature controlled

the ECal ECal Si tracker - 5 layers (axial+stereo), microstrip

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

Adding muon detection capability to exp setup A decay in µ + µ -

10-4 1m-long multy-layers of plastic scintillator + Iron

+ µ - ) Long lived bound state (10 kev binding energy) Decay in

25 Adding muon detection capability to exp setup A decay in µ + µ - Reduced em BG (pion decay only) Pion-pair rejection factor < m-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

26 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)

27 Other searches Nuclear transitions e + e - pairs from magnetic monopole 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

extra U(1)s in string models bottom-up: anomalies associated with dark matter (PAMELA, FERMI) and (g 2)μ Fixed-target

28 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

The Heavy Photon Search experiment at Jefferson Laboratory. A. Celentano (INFN Genova) on behalf of the HPS collaboration

The Heavy Photon Search experiment at Jefferson Laboratory A. Celentano (INFN Genova) on behalf of the HPS collaboration Outline Dark photons: introduction Dark photons searches with fixed-target experiments