PADME: Dark photon search at the Frascati Beam-Test Facility Paolo Valente INFN Roma Ferrara 13/04/15

Outline g’=A’=U Motivation for dark photon searches The dark sector basic model Recent progress on the Dark Photon searches The Frascati linac and the beam-test facility Positron Annihilation into Dark Matter Experiment: the PADME proposal Beam conditions and the Target The electromagnetic calorimeter The dipole magnet The spectrometer The Vacuum chamber Analysis technique for annihilation production Signal selection criteria Positron flux measurement Limit evaluation Experimental technique for bremsstrahlung production Decay in e+e- pair in thin target experiment The dump experiments Conclusion and prospects g’=A’=U Paolo Valente Ferrara 13/04/15

Why a secluded or dark sector? Dark matter, in the strict sense, established since 1930 (Zwicky) Many ideas and models, also more experimental evidence from cosmology Current cosmological “standard” model, LCDM, requires dominant cold dark matter No new particle, beyond the Standard Model, so far from particle physics Problem: connect dark matter (e.g. WIMPs) to SM particles while being compatible with direct measurements: Low elastic cross section on nuclei Low production rates at colliders Solution: DM not directly connected to the SM, but only through “mediator” particles Hidden or secluded or dark sectors often present in string theories and super-symmetry Simple model: add additional U(1)’ gauge group, but a vector boson is not the only possible mediator The mediator could be not the lightest dark particle and thus it is not itself a DM candidate Nuclear recoil too weak MeV GeV TeV Paolo Valente Ferrara 13/04/15

Portals to secluded sector vector dark photon Higgs dark scalar neutrino sterile neutrino axion ALPs Paolo Valente Ferrara 13/04/15

The simplest dark sector model The simplest hidden sector model just introduces one extra U(1) gauge symmetry and a corresponding gauge boson: the “dark photon" or U boson. Two type of interactions with SM particles should be considered As in QED, this will generate new interactions of the type: Not all the SM particles need to be charged under this new symmetry In the most general case qf is different in between leptons and quarks and can even be 0 for quarks. (P. Fayet, Phys. Lett. B 675, 267 (2009).) The coupling constant and the charges can be generated effectively through the kinetic mixing between the QED and the new U(1) gauge bosons In this case qf is just proportional to electric charge and it is equal for both quarks and leptons. e- A’ e+ A’ g Paolo Valente Ferrara 13/04/15

A’ production and decays U boson can be produced in e+ collision on target by: Bremsstrahlung: e+N →e+NA’ Annihilation : e+e-→ gA’ Meson decays If no dark matter candidate lighter than the A’ boson exist: A’→e+e-,m+m-,p+p- the so called “Visible” decays For MA’<200 MeV A’ only decay to e+e- BR(e+e-)=1 If any dark matter c with 2Mc<MA’ exist A’ will dominantly decay into pure dark matter and BR(l+l-) becomes small suppressed by e2 A'→cc ~ 1 so called “Invisible” decays” Paolo Valente Ferrara 13/04/15

Contribution to g-2 from dark photon Muon g-2 SM discrepancy About 3s discrepancy between theory and experiment (3.6s, if taking into account only e+e-hadrons) Contribution to g-2 from dark photon A’ Paolo Valente Ferrara 13/04/15

Dark sector with dark Higgs Model assumes the existence of an elementary dark Higgs h’ boson, which spontaneously breaks the U(1) symmetry. PRD 79, 115008 (2009) U boson can be produced together with a dark Higgs h’ through a Higgs-strahlung e+e-→Uh’ Cross section =20fb x (a/aD)(e2/10-4)(10GeV)2/s For light h’ and U (MU,h’<2Mm) final state with 3(e+e- pair) are predicted Background events with 6 leptons are very rare at this low energies Due to U,h’being very narrow resonances strong kinematical constraints are available on lepton pair masses Experimental search by BaBar and KLOE for U masses above 200 MeV Paolo Valente Ferrara 13/04/15

Experimental status U(1) + dark higgs BaBar Phys. Rev. Lett. 108, 211801 (2012) KLOE-2 arXiv:1501.06795 Production mechanism being bremsstrahlung allows PADME to reach >100MeV A’ masses No data available below 200 MeV in MA’ PADME can provide sensitivity in unexplored parameter region. Paolo Valente Ferrara 13/04/15

Fixed target experiments Radiative background e- Fixed target experiments yield higher luminosity than e+e- collisions but… Main backgrounds: SM Bremsstrahlung Bethe-Heitler Kinematics: A’ takes nearly all the beam energy E0 (sharp peak at x≈1) Electron takes a small energy ≈ mA’ A’ emission almost collinear to the beam: qA’=(mA’/E0)3/2 Electron going at “wide” angle: qe=(mA’/E0)1/2 A’ decay products open by q ≈ mA’/E0 e+ e- e- g Bethe-Heitler background e- e- e+ e- e- E’ E0 Target q qA’ e+ qe E e-

Dark photon experiments Thick target (beam-dump) Absorb all SM backgrounds Look for visible decays Thin target + decay of dark photon: Decay to visible particles (e+ e-, m+ m-, …) “Bump hunting”, looking for a peak in the invariant mass Displaced vertices, looking for long-lived particles Decay to invisible particles Look for missing mass DM particles recoil [Meson decays]

Electron beam-dump experiments Decay region Detector Target Shield Electron energy distribution due to interactions in target and shield Decay probability of g’ after shield ds/dx for g’ production by Bremsstrahlung

Limits from electron beam-dump experiments Beam-dump experiments: looking for decay products of “rare penetrating particles” behind a stopped electron beam SLAC E141 (1987) and E137 (1988), Fermilab E774 (1991) Experiments re-interpreted recently in terms of dark-photon exclusion (e.g. Sarah Andreas) E137 Lshield =179 m Ldecay = 204m 5×109 275 GeV 2×1015 9 GeV 2×1020 20 GeV Nobs = 0 m+m- hadrons

Limits from electron beam-dump experiments decay in dump Lsh E0 Not enough energy E0 Ldec Ne decay too far rate too small INFN CSN1 - LTS1 Workshop - 2014

Dark photon searches in the world A1 @ MAMI WASA @ COSY HADES @ GSI VEPP-III Cornell Phenix @RHIC ATLAS, CMS @ LHC P-348 @ SPS SHIP @ SPS NA48/2 Mu3e @PSI KLOE2 @ DAFNE PADME @ BTF BaBar @ PEP-II JLAB: APEX HPS, DarkLight BDX BelleII SuperKEKB Status: publishing, approved, proposals Paolo Valente Ferrara 13/04/15

Dark photon with thin targets HPS experiment @ JLAB Paolo Valente Ferrara 13/04/15

Dark photons in meson decays Production (kinetic mixing) Decay (No light dark sector) Batell, Pospelov and Ritz PHYS. REV. D 80, 095024 (2009) MA’<Mp0 and no lighter wrt A’ dark sector particle exists: BR(A’→e+e-)=1 Paolo Valente Ferrara 13/04/15

NA48/2 dark photon limit Select p±p0D and p0Dm±n decay Compare data and Monte Carlo Search for unexpected peak in the Mee No excess observed → set a limit in e2 arXiv:1504.00607v1 Paolo Valente Ferrara 13/04/15

Dark photon searches status Favored parameters values explaining g-2 (green band) A’-boson light 10-100 MeV Status of dark photon searches Beam dump experiments (grey) Fixed target Peak search in BG Mesons decays Peaks in M(e+e-) or M(m+m-) Indirect exclusion from ge-2 gm-2 Recent tight limit in blue filled area arXiv:1412.0018v2 Many different techniques, assumptions on dark photon interaction models Kinetic mixing, decay to electrons, no dark sector particles Paolo Valente Ferrara 13/04/15

Status eq≠0 and A’→e+e- g-2 muon band excluded by recent NA48/2 measurement Paolo Valente Ferrara 13/04/15

Meson decays not included the (g-2)m band is not covered any more Status eq=0 and A’→e+e- Meson decays not included the (g-2)m band is not covered any more Paolo Valente Ferrara 13/04/15

Status eq=0 and A’→cc decays Removing the assumption BR(A’→e+e-=1) and introducing dark matter Paolo Valente Ferrara 13/04/15

Why dark photon invisible decays? W. J. Marciano et al. The invisible search technique remove any assumption except coupling to leptons A’ increase its capability of having escaped detection so far No data in the minimal assumptions “If, instead, the A’ decays primarily into invisible light particles (e.g. a pair of dark matter particles with mass < mA’/2), that change would essentially negate all the bounds except those coming from anomalous magnetic moments” arXiv:1402.3620v2 W. J. Marciano et al. arXiv:1402.3620v2 At present there are no MI experimental limit for the A’invisible decay Just a never published ArXiv 0808.0017 by Babar ‘08 with very limited sensitivity on e2 (U3SgU assumes coupling to quarks!) Indirect limit from K+→p+nn (assumes coupling to quarks!) arXiv:1309.5084v1 Paolo Valente Ferrara 13/04/15

Invisible dark photon and kaons In models assuming that the dark photon couples to SM through kinetic mixing eq≠0 K±→p±nn can be used to constrain K±→p±A’ Zd=A’ for Marciano! Depending on how the model is build the limit can change significantly for example allowing the presence of dark Z. Paolo Valente Ferrara 13/04/15

The PADME approach At present all experimental results rely on at least one of the following model dependent assumptions: A’ decays to e+e- (visible decay assumption BR(A’→e+e- = 1) A’ couples with the same strength to all fermions (eq= el) (kinetic mixing) In the most general scenario (PADME) A’ can decay to dark sector particles lighter than the A’ BR(A’→e+e- <<1) Dump and meson decay experiment only limit e2BR(A’→e+e- <<1) A’ can couple to quark with a coupling constant smaller el or even 0 Suppressed or no production at hadronic machines and in mesons decays PADME aims to detect A’ produced in e+e- annihilation and decaying into invisible by searching for missing mass in e+e-→gA’ A’→XX No assumption on the A’ decays products and coupling to quarks Only minimal assumption: A’ bosons couples to leptons PAMDE will limits the coupling of any new light particle produced in e+e- collision (scalars (Hd), vectors (A’ and Zd)) Paolo Valente Ferrara 13/04/15

DAFNE complex in Frascati DAFNE, replacing ADONE (operational until 1993), has been running as e+e- collider at 1,02 GeV since 1999, for KLOE, DEAR, FINUDA, Siddharta, and now KLOE/2 … Synchrotron light source operational with 3 lines (X, UV, IR) High current electron/positron linac + damping ring + test facility Power supplies modulators linac Synchrotron light DAFNE KLOE hall Pumps BTF Cryogenics Power supplies Damping ring Paolo Valente Ferrara 13/04/15

LINAC parameters Design Operational Electron beam final energy 800 MeV 510 MeV Positron beam final energy 550 MeV RF frequency 2856 MHz Positron conversion energy 250 MeV 220 MeV Beam pulse rep. rate 1 to 50 Hz Beam macropulse length 10 nsec 1 to 40 nsec Gun current 8 A Beam spot on positron converter 1 mm norm. Emittance (mm. mrad) 1 (electron) 10 (positron) < 1.5 RMS energy spread 0.5% (electron) 1.0% (positron) electron current on positron converter 5 A 5.2 A Max output electron current >150 mA 350 mA Max output positron current 36 mA 100 mA max Trasport efficiency from capture section to linac end 90% Accelerating structure SLAC-type, CG, 2π/3 RF source 4 x 45 MWp SLED-ed klystrons TH2128C The “shotgun” of the system is of course the high-current linac Paolo Valente Ferrara 13/04/15

The beam test facility BTF LINAC Main rings BTF control room 10 m Power supplies BTF BTF control room Damping Ring transfer line LINAC 10 m transfer line Main rings Paolo Valente Ferrara 13/04/15

DAFNE Beam Test Facility (BTF) Longer Duty Cycle Standard BTF duty cycle = 50*10 ns = 5x10-7 s Already obtained upgrade 50*40ns= 20x10-7 s Work in progress to reach 150 ns (new pulser) … … Up to 250 ns (double phase inversion at the SLED) … … and beyond (no SLED, or SLED detuning), in principle up to 4 ms Energy upgrade planned in 2017. Region from 0-22 MeV can be explored with 550 MeV e+ beam The accessible MA’ region is limited by beam energy e.g. MA’ up to 28 MeV with 750 positron beam 240 ns, 0.5% energy spread achieved at SLAC (same linac) for E-154 experiment Paolo Valente Ferrara 13/04/15

BTF beam summary Energy spread Dp/p ~1% Beam spot: <1 mm RMS Divergence: 1 – 1.5 mrad Effect of multiple scattering and Bremsstrahlung on the Beryllium exit window and in air has to be considered Both size and divergence depend on the optics Beam position: 0.25 mm RMS Pulse duration: 1.5 – 40 ns 10 ns during collider operations Measurement of the beam E spread Beam spot size Beam spot center Beam E spread Nucl. Instrum. Meth. A718 (2013) 107–109 Paolo Valente Ferrara 13/04/15

The PADME experiment 103-104 e+ on target per bunch at 50 bunch/s (1013-1014 e+/year) Basic detector components: Active 50mm diamond target GEM based magnetic spectrometer ~1m length Conventional 0.6T magnet 15 cm radius cylindrical crystal calorimeter with 1x1x20 cm3 crystals 1.75 m Paolo Valente Ferrara 13/04/15

The PADME experiment By C. Capoccia LNF SPAS Paolo Valente Ferrara 13/04/15

The PADME diamond target First BTF test-beam with polycrystalline diamonds: Two 500 mm thick and 4 metal strips: 6.5 mm long and 1.5 mm pitch 300 mm thick 40 graphitized strips 3 mm long, 100 mm width, and 170 mm pitch 50 mm thick, 2×2cm2 sample for first PADME prototype 50 mm thick 5×5mm2 sample for BTF beam diagnostics with Silver Paint 1. 50 mm, silver painted, Estimated CCD=10-20mm 2. Main result of feasibility of 50 mm sensors already established 4. 3. Paolo Valente Ferrara 13/04/15

A possible analyzing magnet for PADME 116 cm 11 to 20 cm gap 52 cm Paolo Valente Ferrara 13/04/15

A possible analyzing magnet for PADME Tapered poles 95 kW 42 kW 16 kW Paolo Valente Ferrara 13/04/15

PADME vacuum vessel study Al 2219 T851 or AL6082 T6 2 mm side walls 4 mm ribs C. Capoccia LNF SPAS Different possibilities under study to minimize the material thickness Different possibilities under study to minimize the material thickness Frascati, Servizio Vuoto V. Lollo, S. Bini Paolo Valente Ferrara 13/04/15

PADME spectrometer Outside Inside trackers trackers vacuum vessel vacuum vessel There is the possibility of having a spectrometer outside the vacuum: Impact on the PADME-visible experiment to be understood Paolo Valente Ferrara 13/04/15

The electromagnetic calorimeter 30 cm Cylindrical shape: radius 150 mm, depth of 200 mm Inner hole 4 cm radius Active volume 13120 cm3 total of 656 crystals 10x10x200 cm3 Material LSO(Ce): high LY, high r, small X0 and RM, short tdecay Material BGO: high LY, high r, small X0 and RM, long tdecay, (free form L3?) Expected performance: s(E)/E =1.1%/√E ⨁ 0.4%/E ⨁1.2% superB calorimeter test at BTF [NIM A 718 (2013) 107–109] s(q) = 3 mm/1.75 m < 2 mrad Angular acceptance 1.5-5 degrees Paolo Valente Ferrara 13/04/15

PADME calorimeter simulation 15 cm long LYSO crystals 20 cm long LYSO crystals Paolo Valente Ferrara 13/04/15

MC calorimeter performance Mmiss2(MeV) Missing mass resolution in agreement with toy MC using s(E)/E =1.1%/√E ⨁ 0.4%/E ⨁1.2% [NIM A 718 (2013) 107–109] Differences are ~ 10% Resolution is the result of combination of angular resolution energy resolution and angle energy correlation due to production Paolo Valente Ferrara 13/04/15

PADME calorimeter from L3 BGO We collected ~80 BGO crystal from L3 calorimeter. We plan to cut them in 4 pieces of 10x10x210 mm3 (up to 240 cells) Plan to test performance with 3x3mm APD and SiPM of 64 channel matrix in 2015 Paolo Valente Ferrara 13/04/15

PADME Geant4 simulation Paolo Valente Ferrara 13/04/15

A PADME BG event (2000 e+) Paolo Valente Ferrara 13/04/15

Improving BG rejection Move the front veto detector inside the beam Thanks to the dispersion included by the dipole magnetic field, a high resolution front detector can enhance the background rejection for events with a positron emitting a soft photon Paolo Valente Ferrara 13/04/15

Search in annihilation production Paolo Valente Ferrara 13/04/15

Experimental technique Spectrometer ECal g P4beam 550 MeV e+ C Target Spectrometer Mmiss2 A’ Search for the process: e+e- → gA’ on target e- at rest electrons (104 550 MeV e+)/bunch beam on a 50 mm diamond target with 50 bunch/s Collect 4x1013 e+ on target in each year of data taking period at BTF (60% eff.) Measure in the ECal the Eg and qg angle wrt to beam direction Compute the Mmiss2 = (P4e- + P4beam - P4g)2 P4e- =(0,0,0,me) and P4beam =(0,0,550,sqrt(5502 + me2)) Paolo Valente Ferrara 13/04/15

Main background sources Geant4 simulation accounts for: Bremsstrahlung, 2 photon annihilation, Ionization processes, Bhabha and Moller scattering, and production ofδ-rays. Custom treatment of e+e-→gg(g) using CalcHep generator. e- e+ g e- e+ g g e+ +1 electron +1 g +2 g e- e+ A’ g Paolo Valente Ferrara 13/04/15

Inclusive signal selection Selection cuts (all decay modes) Only one cluster in EM calo Rejects e+e-→gg final state 5 cm < RCl < 13 cm Improve shower containment Cluster energy within: Emin(MA’) < ECl < 400 MeV Removes low energy bremsstrahlung photons and piled up clusters Positron veto using the spectrometer Ee+< 500 MeV then (Ebeam - Ee+ - Ecl) > 50 MeV Reject BG from bremsstrahlung identifying primary positrons Missing mass in the region: Mmiss2A’±sMmiss2A’ Paolo Valente Ferrara 13/04/15

Background estimates e+e-→ gg(g) e+N→e+Ng Pile up Data Mmiss2 BG sources are: e+e-→gg, e+e-→ggg, e+N→e+Ng, Pile up Pile up contribution is important but rejected by the maximum cluster energy cut and MMiss2. Veto inefficiency at high missing mass (E(e+)≃ E(e+)beam) New Veto detector introduced to reject residual BG New sensitivity estimate ongoing Paolo Valente Ferrara 13/04/15

PADME invisible sensitivity estimate Based on 1x1011 fully GEANT4 simulated e+ on target events Number of BG events is extrapolated to 4x1013 electrons on target Using N(A’g)=s(NBG) d enhancement factor d(MA’) = s(A’g)/s(gg) with e=1 M. Raggi, V. Kozhuharov Adv. in HEP Vol. 2014 ID 959802, Paolo Valente Ferrara 13/04/15

Search in bremsstrahlung production Paolo Valente Ferrara 13/04/15

Visible search experiment e- beam Visible search experiment Spectrometer ECal e- 750 MeV e- Target e+ Spectrometer Search for the process: e-N → Ne-A’ →Ne-e-e+ 750 MeV electron beam on a ~0.5 mm tungsten target Measure in the spectrometer only the P4e- P4e+ Compute the MA’2 = (P4e- + P4e+)2 and decay vertex position Search for peaks in the e+e- invariant mass Paolo Valente Ferrara 13/04/15

Indication on visible decay sensitivity ??PADME?? with e=1・10-3 Production cross section calculated with MADGraph code Final state is more constrained by invariant mass of the e+e- pair Indication of a limit down to e2 ~10-7 is expected at low masses Density of tracks in the spectrometer is the crucial point to be clarified Design of the spectrometer not yet finalized Paolo Valente Ferrara 13/04/15

Electron dumps experiments PADME dump W 1.2 2・1020 ~30 C ~0.1 1 By S. Andreas PADME dump 1017 750MeV e- Paolo Valente Ferrara 13/04/15

High intensity Radioprotection limit: <n> = 3.125×1010 particles/s Typical charge to damping ring: >1 nC/pulse for e- 0.7-0.8 nC/pulse for e+ But… Much higher charge on positron converter 8 A (12 A) from gun cathode A few measurements on the maximum LINAC charge, driven by beam-dump experiments requirements Paolo Valente Ferrara 13/04/15

Bunch charge vs. length E = 725 MeV ×4 increasing pulse length +30% Decreasing grid stopping potential ×3 - ×5 Increasing gun pulse height 10 ns 10 ns Trying to put all together: WCM readout saturated at 16 nC…

How many electrons on target? Let’s compute how many eot/y* for 10 nC/pulse so we can scale easily with the charge available from the LINAC 10 nC = 10-8/1.6×10-19 = 6.25×1010 At 49 Hz (1 pulse to spectrometer line) = 3×1012 e/s 2 orders of magnitude more than present BTF authorization Standard year = 1 y*= 120 days at 100% efficiency (107 s) 3.175×1019 eot/y* 25 nC translates in 0.8×1020 eot/y* Considering measurements at 725 MeV, 40 ns, in the present LINAC configuration and quite conservative assumptions Further extension of the pulse to 150 ns seems feasible with the present RF configuration, and should bring us to ≈100 nC, i.e. 3×1020 eot/y* Where can we dump 3×1012 to 3×1013 e/s ? Paolo Valente Ferrara 13/04/15

LINAC beam dump 50 cm 30 cm 25 cm Paolo Valente Ferrara 13/04/15

LINAC beam dump DHPTT01 A new thin vacuum chamber for DHPTT01 with a double exit Exactly the same design of DHPTT02 A straight vacuum pipe to the inside of the cavity Possibly, use DR pumps hall for dump experiments DHPTT02 DR pumps hall Paolo Valente Ferrara 13/04/15

PADME dump toy Monte Carlo Try to evaluate driving design parameters for the PADME dump Toymc includes: Production cross section calculated by MADgraph (thanks to A. Celentano) Evaluate the produced number of dark photons Scale by decay length acceptance Scale by electron acceptance in the detector using kinematical distribution from a toy Distribution have been compared with MADGraph for several MU Not yet implemented in depth production of the A’ Next plot not to be considered exclusions still Paolo Valente Ferrara 13/04/15

PADME dump main parameters Dark photon production 1 2 3 4 5 ±10 cm at 1m Electron angular acceptance Decay length acceptance applied Decay into the dump e+e- out of Acc Paolo Valente Ferrara 13/04/15

Dump comparison Zero BG hypothesis, in depth production to be refined, not yet a sensitivity plot NA48/2 BaBar e- DUMP Now e- DUMP PADME ee PADME mm Real case e- DUMP E137 1・1020, 1.2 GeV electrons; 20 cm aperture at 50 cm from 8 cm W dump Paolo Valente Ferrara 13/04/15

BDX @ LNF A. Celentano, talk at “ What Next LNF” Same acceptance limit at 100 MeV coming from low beam energy aD=0.1 mc=10 MeV Beam energy 1.2 GeV (e-) CsI detector 60×60×225 cm3 built with crystals from dismounted BaBar ECal? Paolo Valente Ferrara 13/04/15

Energy upgrade ±10 cm at 1m Paolo Valente Ferrara 13/04/15

BTF upgrade Decays to lepton pairs Decays to invisible Energy ~√E PADME 1013 eot PADME 1013 eot e+ 550 MeV e+ 750 MeV e+ 1 GeV Energy Duty cycle Energy Intensity Duty cycle PADME dump 1016 eot Energy Intensity Paolo Valente Ferrara 13/04/15

15 m

Add 4 sections + 2 SLED-ed klystrons +320 MeV: Reach: 1070 MeV electrons 870 MeV positrons Paolo Valente Ferrara 13/04/15

Add 4 sections + 4 SLED-ed klystrons +180 MeV: +320 MeV: Reach: 1250 MeV electrons 1050 MeV positrons Add two more SLED-ed klystrons and split power only in two sections instead of four Paolo Valente Ferrara 13/04/15

PADME project plans Project has been presented as a “What Next” Project in INFN CSN1 The project has received positive comments form CSN1 referees Proposal for R&D financing will be discussed in the next CSN1 meeting Proto collaboration formed including LNF, Rome1, Lecce and Sofia university 6 weeks test beam time asked at DAFNE BTF in 2015 Study the prototype of BGO calorimeter solution (L3 crystals) Test diamond target prototypes Study the maximum beam current per bunch and beam spot size Optimize beam characteristics for PADME operation bunch length, number of particle per bunch, background, beam positioning stability Interesting synergy with BDX project identified (BDX at LNF?) Many item still to be covered! Search for more collaborators started Paolo Valente Ferrara 13/04/15

PADME kick-off meeting PADME website http://www.lnf.infn.it/acceleratori/padme/index.html Paolo Valente Ferrara 13/04/15

Outlook and plans An experiment running at DAFNE BTF sensitive to both A’→invisible and A’→e+e- decays has been proposed to INFN CSN1 Exclusion limit in e2 down to 1-2・10-6 can be achieved in invisible decays with the present BTF beam parameters in the region MA’ 2- 22 MeV M. Raggi and V. Kozhuharov, Advances in High Energy Physics Vol. 2014 ID 959802, Possible accessible regions for a bremsstrahlung produced A’→e+e- were identified to reach ~100MeV Detailed study of the sensitivity in this channel are ongoing Beam dump experiment searching for both visible and invisible Dark photon decays are also possible. In all the cases an energy upgrade of the Linac is a plus Paolo Valente Ferrara 13/04/15

“The hardest thing of all is to find a black cat in a dark room, especially if there is no cat” Confucius Paolo Valente Ferrara 13/04/15