• GOAL • BDX EXPERIMENT OVERVIEW: • BDX @ JLAB • DETECTOR • BACKGROUNDS • BDX STATUS • BDX UPDATE • MUON FLUX MEASUREMENTS Status of the B Dx experiment Mariangela Bond ì for the BDX Collaboration HPS Collaboration meeting - JLAB, May 22-24, 2018
The X (in-)elastically scatters on a e-/nucleon in the detector producing a visible recoil An electron radiates an A’ and the A’ promptly decays to a X pair GeV - high intensity e- beam B Dx experiment GOAL : Light Dark Matter search in a beam Dump experiment 𝟁 production 𝟁 detection √α D ε e 1 Step: LDM production 2 Step : LDM detection 1
- High energy beam : 11 GeV - the Highest available beam current ~ 65 μA - Integrated charge: 10 22 EOT in ~ 10 months • BDX detector located underground, downstream of Hall-A beam-dump • BDX beamtime fits the Hall-A experimental program (already-approved experiments with more than 1022 (11 GeV) EOT, e.g. Moeller exp.) • New underground experimental hall B Dx @ JLA B Key points: NEW existing 2
X-electron -> EM shower ~ GEV WLS fibres + SiPM PMTs/SiPM LightGuide/WLS scint. Plastic scintillators Plastic scintillators •6x6 mm 2 SiPM readout •8 modules 10x10 crystals each •800 CsI(Tl) crystals (from BaBar EMCal) B Dx detector LDM signal in the Detector : LDM detection Modular EM calorimeter • ̴ 3 m long , ̴ 50x50 cm 2 front face Background rejection INNER VETO Lead vault 5cm thick OUTER VETO 3
CsI(Tl) crystals + SiPMs Inner Veto: plastic scint. + WLS + SiPM Inner Veto in the lead vault Outer Veto: plastic scint. + Light guide + PMT Outer Veto: plastic + WLS plastic + PMT conservatively experimental data to full detector. B Dx Prototype Goals: 1) validate the proposed design and technical choices 2) measure the capability of rejecting cosmic background and project 4
cuts and extrapolation to 1022 EOT ~ 10 ν. expected cosmic bg in the BDX lifetime < 2 counts statistics of 2.2×108 EOT we obtained, after all rejection location The interaction of the 11 GeV electron beam in the dump was simulated and the flux of secondaries was studied as a function of the distance from the dump Using Vetos in anti-coincidence and high energy thresholds O(0.5GeV): B ackground Cosmic Background : measured with the BDX prototype in Catania/LNS Rate measured in one crystal Data/Sim comparison Beam-related Background : BD χ detector ๏ No μ n and γ with E>500 MeV are found at detector ๏ Neutrinos survives to the detector -> For a simulated Closed symbols: FLUKA Open symbols: GEANT4 5 20.6
BDX Proposal to JLAB PAC 44 (2016) BDX Proposal Update to JLAB PAC 45 (2017) Assessing the beam-related bg : •measuring the muon flux behind the Hall-A dump with the current shielding configuration •compare MC results obtained in two frameworks: Geant4 and FLUKA (in col with RadCon) report results/simulation of Muon test B DX status • C2 - Conditionally Approval • Main concern expressed by the PAC on beam-on background BDX Proposal to JLAB PAC46 (2018) 6
configuration when 11 GeV e- -beam is on the hall A beam-dump with the current shielding and helping to understand background drilled down to beam height (8 m) and aligned with the beam-line n 2 different positions B ( 25 m) and C (28 m) B DX Muon test ๏ We have measured the flux of high-energy muon behind ๏ The measurements is a benchmark for MC simulation ๏ 2 10” pipes downstream of Hall-A beam-dump were B C Today some time ago … B C 7
B DX Muon test : B DX-HODO detector same technologies proposed in the final experiment � CRISTAL ๏ CsI(Tl) crystal ( 5x5 x 30 cm 2 ) ๏ 6x6 mm2 Hamamatsu SiPMs � SCINTILLATORS ๏ 13 plastic scintillator paddles 1 cm thick ๏ 3x3 mm2 SIPM coupled via WLS fibers � CONTAINER ๏ Cylindrical vessel (d=20cm, h=52cm) ๏ Stainless steel, water-tight 8
DATA taking Connecting the extension sections The equipped tent B DX Muon test new Hall-T ent detector 8 m down e d i s n i O D O H B - X l l D e w B e h T 9
measurable !) framework •BDX-HODO response with GEANT4 GEANT4 •propagating muons to the pipe positions using on Hall-A beam dump (FLUKA) •generating muons by primary electron interaction B DX Muon test Expected results: MC simulation Expected particle flux (FLUKA) and energy deposition in the CsI(Tl) crystal in location B ✦ Simulation performed using FLUKA/GEANT4 All particles μ Deposited energy neutrons ✦ Only muons and neutrons reach the area of interest Particle flux All particles ✦ Rate from cosmic muons is negligible (and μ 10
Δρ ~ 2.5% -> Δrate ~ 60% •Rate Well B: order of magnitude of kHz Flux vs vertical position •generating muons by primary electron interaction on Hall-A beam dump (FLUKA) •propagating muons to the pipe positions using GEANT4 •BDX-HODO response with GEANT4 of interest •Rate Well C: order of magnitude of Hz •Rate_WellB/Rate_WellC ~ 200-400 ρsoil = 1.9 ρsoil = 1.95 Δρ ~ 2.5% -> Δrate ~ 30% ρsoil = 1.9 ρsoil = 1.95 B DX Muon test Expected results: MC simulation ✦ Simulation performed using FLUKA/GEANT4 framework ) -2 cm -1 Well b A µ Flux (Hz 1 − 1 Conc. 2.4 - Dirt 1.9 10 Conc. 2.4 - Dirt 1.92 Conc. 2.4 - Dirt 1.95 ✦ Only muons and low-energy neutrons reach the area Conc. 2.35 - Dirt 1.95 Conc. 2.3 - Dirt 1.95 Conc. 2.25 - Dirt 1.97 Conc. 2.2 - Dirt 1.99 − 2 10 ✦ Rate from cosmic muons is negligible (and measurable !) 0 20 40 60 80 100 120 140 160 R (cm) ✦ Significant dependence on soil density : − 1 10 ) -2 cm Well C -1 • soil density measured in correspondence of the two wells : 1.93 - 1.95 g/cm3 A µ Flux (Hz • soil density along the muon flight path unknown : constant ?? 2 − 10 • concrete density: no measurement available ✦ Expected Rate : − 3 10 Conc. 2.4 - Dirt 1.9 Conc. 2.4 - Dirt 1.92 Conc. 2.4 - Dirt 1.95 − 4 Conc. 2.35 - Dirt 1.95 10 Conc. 2.3 - dirt 1.95 Conc. 2.25 - Dirt 1.97 Conc 2.2 - dirt 1.99 0 20 40 60 80 100 120 140 160 R (cm) 11
� Well C: 14 positions (ranged between -80 cm and 80 cm). Each measurement was repeated changing the current . ★ Cosmic Background ★ Positions scan: the muon flux sampled at different heights with respect to nominal beam height ( 8 m underground). �Well1 : 1 position (position 0) � Well B : 22 positions (ranged between -110 cm and 150 cm). Each measurement was repeated at least 2 times � Current = 2.2uA, 5uA, 10uA, 22uA at least 2 times ★ Currents scan: the muon flux sampled at nominal beam height ( 8 m underground) B DX Muon test Experimental Campaign ๏ Beam: CEBAF e- beam @ 10.6 GeV and current of 22 uA ๏ Beam: CEBAF e- beam @ 10.6 GeV ๏ Long run taken with BDX-HODO inside Well C 12
B DX Muon test Hall-A beam current - outside temperature variation (ΔΤ ~ 30 o C) detector temperature stable in spite of BDX-HODO temperature monitoring on-line - Sun/Snow/ Storm Beam-on trigger rate ~ 10 kHz Well B - Pos 0 Running the Experiment First muon signal on the scope 22 Beam current (µA) 29 27 25 23 Detector Temperature (°C) 21 11 19 17 15 13 11 9 7 0 19:40 19:55 20:09 20:24 20:38 20:52 21:07 21:21 21:36 5 0:00 4:48 9:36 14:24 19:12 0:00 Time Time 13
(Front - Crystal - Back coincidence) measured by a marked tape attached on the PVC extinction Angular alignment performed looking at the rate as a function of rotating angle θ θ Well B Pos 0 Rate B DX Muon test first muon signal on the scope Running the Experiment ✦ Vertical position inside the pipe ✦ Rate [Hz] Rate[Hz] 8000 7000 Beam direction 6000 height 5000 4000 14 − 20 − 10 0 10 20 30 40 Theta Theta
(Front - Crystal - Back coincidence) Crystal spectrum (Front - Crystal - Back coincidence) Crystal spectrum the background with a Fermi function convoluted with a gaussian function while cleaned excluding the beam-trip B DX Muon test Experimental Results Rate(Hz) ✦ In phase of analysis, the data have been 2 10 ✦ Red histo: events analyzed 10 1 − 12 × 10 Muons/(MeV*EOT) 6 0 1000 2000 3000 4000 5000 6000 7000 8000 T(s) 5 Muons/(MeV*EOT) 4 11 − 10 3 12 − 10 2 − 13 10 1 14 − 10 0 10 20 30 40 50 60 70 80 90 100 − 15 10 E[MeV] ✦ The peak is fitted by Landau function 16 − 10 17 − 10 0 20 40 60 80 100 120 ✦ Rate extracted integrating the green fit E[MeV] 15
Crystal spectrum Crystal spectrum ★Front/Back/crystal coincidence rate is ~ 0.1 Hz -> Negligible ★No significant effect of cosmic muons on rates measured with beam-on ★Reduction factor between TEDF and well is ~ 2.5 (Front sc. - Crystal - Back sc. coincidence) B DX Muon test Cosmic B ackground Hz/MeV Hz/MeV TEDF TEDF 1 well2 well2 − 2 10 1 − 10 3 − 10 − 2 10 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 E[MeV] E[MeV] ✦ Black spectrum: measurement without shielding performed at TEDF building ✦ Blue spectrum: measurement inside well C at 0 position 16
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