PADME project at DAFNE BTF part 2 Mauro

PADME project at DAFNE BTF (part 2) Mauro Raggi & Paolo Valente Seminario INFN Sezione di Perugia, 9 Marzo 2015 PADME website http: //www. lnf. infn. it/acceleratori/padme/index. html

Outline The dark sector basic model Motivation for dark photon searches Recent results on the Dark Photon searches Positron Annihilation into Dark Matter Experiment 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 M. Raggi and P. Valente Perugia 09/03/15

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: e. A’ e+ 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 g A’ In this case qf is just proportional to electric charge and it is equal for both quarks and leptons. M. Raggi and P. Valente Perugia 09/03/15

A’ production and decays U boson can be produced in e+ collision on target by: Bremsstrahlung: e+N →e+NA’ Annihilation : e+e-→ g. A’ 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’<210 Me. V A’ only decay to e+e- BR(e+e-)=1 If any dark matter c with 2 Mc<MA’ exist A’ will dominantly decay into pure dark matter and BR(l+l-) becomes small suppressed by e 2 A'→cc ~ 1 so called “Invisible” decays” M. Raggi and P. Valente Perugia 09/03/15

Positron excess in cosmic rays Positron excess: PAMELA, FERMI, AMS 02 No significant excess in antiprotons Consistent with pure secondary production Leptofilic low mass dark matter annihilation? M. Raggi and P. Valente Perugia 09/03/15

Hints for dark matter annihilation? c A’ е+ е- е. A’ c е+ g' е+ A', . . е- If Dark Matter is the explanation to the positron excess, then the mediator should be light ( < 2*Mproton) Coupling constant to DM could be arbitrary (even О(1)) The Lagrangian term can arise through Fermions being charged (mili) under this new gauge symmetry (qf � 0 for some flavors) Kinetic mixing between ordinary photon and DM one Using simply an effective description: M. Raggi and P. Valente Perugia 09/03/15

Muon g-2 SM discrepancy About 3 s discrepancy between theory and experiment (3. 6 s, if taking into account only e+ e- � hadrons) Contribution to g-2 from dark photon A’ M. Raggi and P. Valente Perugia 09/03/15

The DAMA-Libra effect ar. Xiv: 1401. 3295 v 1 A’ Nuclear recoil by the exchange of a dark photon radiopure Na. I (Tl) Independent of c mass value M. Raggi and P. Valente Perugia 09/03/15

Observation of 3. 5 Ke. V X-ray line Recently a 3. 55 Ke. V X-ray line (~3 s) has been reported in the stacks analysis of 73 galaxy clusters from the XMM-Newton telescope ar. Xiv: 1402. 2301 v 1 A similar analysis finds an evidence at the 4. 4 s level for a 3. 52 Ke. V line from the analysis of the X-ray spectrum of the Andromeda galaxy (M 31) and the Perseus Cluster ar. Xiv: 1402. 4119 ar. Xiv: 1402. 2301 v 1 M. Raggi and P. Valente ar. Xiv: 1402. 4119 Perugia 09/03/15

U(1) symmetry explanation Many models have been developed to explain such a line based on sterile neutrinos A possible explanation of such a line in term of the U(1) gauge theory with an Higgs mechanism is proposed in ar. Xiv: 1404. 2220 v 1 A single new scalar dark matter field f of mass 7. 1 Ke. V is introduced f couples to SM Higgs through A’ boson Due to the very small mass f can only decay into gg or nn creating the Xray line at 3. 5 Ke. V After spontaneous symmetry breaking of the U(1) symmetry the A’ boson becomes massive Due to constraints coming from the relic abundance a mass interval has been identified by authors for the A’ boson mass 7 Ke. V<MA’<10 Me. V M. Raggi and P. Valente Perugia 09/03/15

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 Higgsstrahlung e+e-→Uh’ Cross section =20 fb x (a/a. D)(e 2/10 -4)(10 Ge. V)2/s For light h’ and U (MU, h’<2 Mm) 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 Ba. Bar and KLOE for U masses above 200 Me. V M. Raggi and P. Valente Perugia 09/03/15

Experimental status U(1) + dark higgs Ba. Bar Phys. Rev. Lett. 108, 211801 (2012) KLOE-2 ar. Xiv: 1501. 06795 Production mechanism being bremsstrahlung allows PADME to reach >100 Me. V A’ masses No data available below 200 Me. V in MA’ PADME can provide sensitivity in unexplored parameter region. M. Raggi and P. Valente Perugia 09/03/15

Dark photon searches in the world A 1 @ MAMI WASA @ COSY HADES @ GSI VEPP-III Cornell Phenix @RHIC ATLAS, CMS @ LHC P-348 @ SPS KLOE 2 @ DAFNE SHIP @ SPS Ba. Bar @ PEP-II JLAB: APEX PADME @ BTF NA 48/2 HPS, Mu 3 e @PSI Dark. Light BDX Belle. II Super. KEKB Status: publishing, approved, proposals M. Raggi and P. Valente Perugia 09/03/15

Dark photon with thin targets e+ Target EBeam qe EA’ ≈ E 0 q. A’ q e- Ee ≈ m. A’ HPS experiment M. Raggi and P. Valente Perugia 09/03/15

Dark photon in dump experiments de cay in d um p Lsh Dump in a nutshell E 0 Ne ~ 1020/year N 0 ~ 6 x 1023 rate too small M. Raggi and P. Valente E 0 decay too far Perugia 09/03/15 Decay product acc Ne Ldec

E 137 at SLAC (1980 -1982) Al target ~2 x 1020 20 Ge. V e- on target Lshield =179 m Ldecay = 204 m Nobs = 0 Experiment reinterpreted by S. Andeas M. Raggi and P. Valente Perugia 09/03/15

Dark photons in meson decays Production (kinetic mixing) Decay (No light dark sector) Batell, Pospelov and Ritz PHYS. REV. D 80, 095024 (2009) MA’<Mp 0 and no lighter wrt A’ dark sector particles exist BR(A’→e+e-)=1 M. Raggi and P. Valente Perugia 09/03/15

NA 48/2 dark photon limit Select p±p 0 D decay Compare data and montecarlo Search for unexpected peak in the Mee No excess observed → set a limit in e 2 M. Raggi and P. Valente Perugia 09/03/15

Dark photon searches status Favored parameters values explaining g-2 (green band) A’-boson light 10 -100 Me. V 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 ar. Xiv: 1412. 0018 v 2 Recent tight limit in blue filled area Many different techniques, assumptions on dark photon interaction models Kinetic mixing, decay to electrons, no dark sector particles M. Raggi and P. Valente Perugia 09/03/15

Status eq≠ 0 and A’→e+e- g-2 muon band excluded by recent NA 48/2 measurement M. Raggi and P. Valente Perugia 09/03/15

Status eq=0 and A’→e+e- Meson decays not included the (g-2)m band is not covered any more M. Raggi and P. Valente Perugia 09/03/15

Status eq=0 and A’→cc decays Removing the assumption BR(A’→e+e-=1) and introducing dark matter M. Raggi and P. Valente Perugia 09/03/15

Why dark photon invisible decays? The invisible search technique remove any assumption except coupling to leptons W. J. Marciano et al. 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 < m /2), that change would essentially negate all. A’ the bounds except those coming from anomalous magnetic moments” ar. Xiv: 1402. 3620 v 2 W. J. Marciano et al. ar. Xiv: 1402. 3620 v 2 At present there are no MI experimental limit for the A’� invisible decay Just a never published Ar. Xiv 0808. 0017 by Babar ‘ 08 with very limited sensitivity on e 2 (U 3 S� g. U assumes coupling to quarks!) Indirect limit from K+→p+nn (assumes coupling to quarks!) ar. Xiv: 1309. 5084 v 1 M. Raggi and P. Valente Perugia 09/03/15

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. M. Raggi and P. Valente Perugia 09/03/15

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 e 2 BR(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-→g. A’ 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)) M. Raggi and P. Valente Perugia 09/03/15

DAFNE Beam Test Facility (BTF) NIM A 515 (2003) 524– 542 electrons Maximum energy [Me. V] 750 Me. V Linac energy spread Typical Charge [n. C] positrons 550 Me. V 0. 5% 2 n. C Bunch length [ns] 1% 0. 85 n. C 1. 5 - 40 Linac Repetition rate 1 -50 Hz Typical emittance [mm mrad] 1 ~10 Beam spot s [mm] 1 mm Beam divergence 1 -1. 5 mrad Longer Duty Cycle Standard BTF duty cycle = 50*10 ns = 5 x 10 -7 s Already obtained upgrade 50*40 ns= 20 x 10 -7 s (Thanks to BTF team) Work in progress to exceed 100 ns The accessible MA’ region is limited by beam energy Region from 0 -22 Me. V can be explored with 550 Me. V e+ beam M. Raggi and P. Valente Perugia 09/03/15

The PADME experiment 103 -104 e+ on target per bunch at 50 bunch/s (1013 -1014 e+/year) Basic detector components: Active 50 mm diamond target GEM based magnetic spectrometer ~1 m length Conventional 0. 6 T magnet 1. 75 m 15 cm radius cylindrical crystal calorimeter with 1 x 1 x 20 cm 3 crystals M. Raggi and P. Valente Perugia 09/03/15

The PADME experiment By C. Capoccia LNF SPAS M. Raggi and P. Valente Perugia 09/03/15

The PADME diamond target First BTF test-beam with polycrystalline diamonds: 1. 2. 3. 4. 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× 2 cm 2 sample for first PADME prototype 50 mm thick 5× 5 mm 2 sample for BTF beam diagnostics with Silver Paint 1. 50 mm, silver painted, Estimated CCD=10 -20 mm 2. Main result of feasibility of 50 mm sensors already established 3. M. Raggi and P. Valente 4. Perugia 09/03/15

A possible analyzing magnet for PADME 116 cm 11 to 20 cm gap 52 cm M. Raggi & P. Valente Perugia, 9/3/2015 30

A possible analyzing magnet for PADME Tapered poles 95 k. W 42 k. W 16 k. W M. Raggi & P. Valente Perugia, 9/3/2015 31

PADME vacuum vessel study Al 2219 T 851 or AL 6082 T 6 2 mm side walls 4 mm ribs C. Capoccia LNF SPAS Different possibilities under study to minimize the material thickness Frascati, Servizio Vuoto V. Lollo, S. Bini M. Raggi and P. Valente Perugia 09/03/15

PAMDE spectrometer trackers vacuum vessel trackers Outside Inside There is the possibility of having a spectrometer outside the vacuum: Impact on the PADME-visible experiment to be understood M. Raggi and P. Valente Perugia 09/03/15

The electromagnetic calorimeter 30 cm Cylindrical shape: radius 150 mm, depth of 200 mm Inner hole 4 cm radius Active volume 13120 cm 3 total of 656 crystals 10 x 200 cm 3 Material LSO(Ce): high LY, high r, small X 0 and RM, short tdecay Material BGO: high LY, high r, small X 0 and RM, long tdecay, (free form L 3? ) Expected performance: s(E)/E =1. 1%/√E � 0. 4%/E � 1. 2% s(q) = 3 mm/1. 75 m < 2 mrad Angular acceptance 1. 5 -5 degrees M. Raggi and P. Valente super. B calorimeter test [NIM at BTF A 718 (2013) 107– 109] Perugia 09/03/15

PADME calorimeter simulation 15 cm long LYSO crystals 20 cm long LYSO crystals M. Raggi and P. Valente Perugia 09/03/15

MC calorimeter performance Mmiss 2(Me. V) 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 M. Raggi and P. Valente Perugia 09/03/15

PADME ecal using L 3 BGO crystals We collected ~80 BGO crystal from L 3 calorimeter. We plan to cut them in 4 pieces of 10 x 210 mm 3 (up to 240 ecal cells already in our hands!) Plan to test performance with 3 x 3 mm APD and Si. PM of 64 ch matrix in 2015 M. Raggi and P. Valente Perugia 09/03/15

PADME geant 4 simulation M. Raggi and P. Valente Perugia 09/03/15

A PADME BG event (2000 e+) M. Raggi and P. Valente Perugia 09/03/15

Search in annihilation production M. Raggi and P. Valente Perugia 09/03/15

Experimental technique ECal Spectrometer g P 4 beam 550 Me. V e+ C Target Spectrometer 2 s s i Mm A’ Search for the process: e+e- → g. A’ on target e- at rest electrons (104 550 Me. V e+)/bunch beam on a 50 mm diamond target with 50 bunch/s Collect 4 x 1013 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 Mmiss 2 = (P 4 e- + P 4 beam - P 4 g)2 P 4 e- =(0, 0, 0, me) and P 4 beam =(0, 0, 550, sqrt(5502 + me 2)) M. Raggi and P. Valente Perugia 09/03/15

Main background sources Geant 4 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 Calc. Hep generator. e- g g e+ g g e- g e+ +1 electron g e+ +1 g +2 g e. A’ e+ g M. Raggi and P. Valente Perugia 09/03/15

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 Me. V Removes low energy bremsstrahlung photons and piled up clusters Positron veto using the spectrometer Ee+< 500 Me. V then (Ebeam - Ee+ - Ecl) > 50 Me. V Reject BG from bremsstrahlung identifying primary positrons Missing mass in the region: Mmiss 2 A’±s. Mmiss 2 A’ M. Raggi and P. Valente Perugia 09/03/15

Background estimates Data Mmiss 2 + + e+e-→ gg(g) e N→e Ng Pile up BG sources are: e+e-→gg, e+e-→ggg, e+N→e+Ng, Pile up contribution is important but rejected by the maximum cluster energy cut and MMiss 2. Veto inefficiency at high missing mass (E(e+)≃ E(e+)beam) New Veto detector introduced to reject residual BG New sensitivity estimate ongoing M. Raggi and P. Valente Perugia 09/03/15

PADME invisible sensitivity estimate Based on 1 x 1011 fully GEANT 4 simulated e+ on target events Number of BG events is extrapolated to 4 x 1013 electrons on target Using N(A’g)=s(NBG) d enhancement factor d(MA’) = s(A’g)/s(gg) with e=1 PADME invisible sensitivity M. Raggi, V. Kozhuharov Advances in High Energy Physics Vol. 2014 ID 959802, M. Raggi and P. Valente Perugia 09/03/15

Search in bremsstrahlung production M. Raggi and P. Valente Perugia 09/03/15

Visible search experiment Spectrometer ECal e 750 Me. V e- e- beam Target Spectrometer e+ Search for the process: e-N → Ne-A’ →Ne-e-e+ 750 Me. V electron beam on a ~0. 5 mm tungsten target Measure in the spectrometer only the P 4 e- P 4 e+ Compute the MA’ 2 = (P 4 e- + P 4 e+)2 and decay vertex position Search for peaks in the e+e- invariant mass M. Raggi and P. Valente Perugia 09/03/15

Indication on visible decay sensitivity with e=1・ 10 -3 ? ? PADME? ? 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 e 2 ~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 M. Raggi and P. Valente Perugia 09/03/15

Electron dumps experiments PADME dump W 1. 2 2・ 1020 ~30 C ~0. 1 1 By S. Andreas PADME dump 1017 750 Me. V e- M. Raggi and P. Valente Perugia 09/03/15

PADME dump toymc 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 M. Raggi and P. Valente Perugia 09/03/15

PADME dump main parameters Dark photon production 5 4 ± 10 cm at 1 m 3 2 1 0 Decay length acceptance applied Electron angular acceptance Decay into the dump e+e- out of Acc M. Raggi and P. Valente Perugia 09/03/15

Dump comparison Zero BG hypothesis, in depth production to be refined, not yet a sensitivity plot NA 48/2 Ba. Bar Now e- PADME ee DUMP PADME mm Real case e. DUMP E 137 1・ 1020, 1. 2 Ge. V electrons; 20 cm aperture at 50 cm from 8 cm W dump M. Raggi and P. Valente Perugia 09/03/15

BDX @ LNF A. Celentano, talk at “ What Next LNF” Same acceptance limit at 100 Me. V coming from low beam energy a. D=0. 1 mc=10 Me. V Beam energy 1. 2 Ge. V (e-) Cs. I detector 60× 225 cm 3 built with crystals from dismounted Ba. Bar ECal? M. Raggi and P. Valente Perugia 09/03/15

PADME project plans Project has been presented as a “What Next” Project in INFN CSN 1 The project has received positive comments form CSN 1 referees Proposal for R&D financing will be discussed in the next CSN 1 meeting Proto collaboration formed including LNF, Rome 1, Lecce and Sofia university 6 weeks test beam time asked at DAFNE BTF in 2015 Study the prototype of BGO calorimeter solution (L 3 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 M. Raggi and P. Valente Perugia 09/03/15

PADME kick-off meeting PADME website http: //www. lnf. infn. it/acceleratori/padme/index. html M. Raggi and P. Valente Perugia 09/03/15

Conclusions and plans An experiment running at DAFNE BTF sensitive to both A’→invisible and A’→e+e- decays has been proposed to INFN CSN 1 Exclusion limit in e 2 down to 1 -2・ 10 -6 can be achieved in invisible decays with the present BTF beam parameters in the region MA’ 2 -22 Me. V M. Raggi and V. Kozhuharov, Advances in High Energy Physics Vol. 2014 ID 959802, Possible accessible regions for a bremsstrahlung produced A’→e+ewere identified to reach ~100 Me. V 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 will be desirable M. Raggi and P. Valente Perugia 09/03/15

SPARE SLIDES M. Raggi and P. Valente Perugia 09/03/15