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NA64 Dipanwita Banerjee ETH, Zurich On behalf of the NA64 - PowerPoint PPT Presentation

Dec 02, 2023 •521 likes •766 views

NA64 Dipanwita Banerjee ETH, Zurich On behalf of the NA64 collaboration NA64 Collaboration NA64: Search for dark sector physics in missing energy events Approved in March 2016 for the A > invisible decay search with electron

  1. NA64 Dipanwita Banerjee ETH, Zurich On behalf of the NA64 collaboration

  2. NA64 Collaboration

  3. NA64: Search for dark sector physics in missing energy events • Approved in March 2016 for the A’ —> invisible decay search with electron beam. • Two runs in 2016 —>focus on the A’ parameter space suggested for the (g-2) μ anomaly. • First results from the two weeks beam time in July’2016 published, most of the (g-2) μ favoured parameter space excluded. • 10 times more statistic acquired in October’2016. Analysis in progress.

  4. NA64: Setup Key Features of the setup:

  5. NA64: Search for dark sector physics in missing energy events tracker/SR tagging Missing momentum ECAL 𝞇 e - beam A’ HCAL 𝞇 VETO Selection of 100 GeV electrons NA64 —> fixed target experiment combining the active beam dump technique with missing energy measurement searching for invisible decays of massive A’ produced in the reaction eZ—> eZA’ of electrons scattering off a nuclei (A,Z), with a mixing strength 10 -6 < 𝜻 < 10 -3 and masses M A’ ~ sub-GeV range. 100 GeV electrons dumped against an ECAL, a sandwich of lead and scintillators (34 X 0 ), to produce massive A’ through scattering with the heavy nuclei. The typical signature for a signal will be missing energy in the ECAL and no activity in the the VETO and HCAL. Background from hadrons, muons and low energy electrons must be rejected upstream.

  6. NA64: Search for dark sector physics in missing energy events A´ spectra, 100 GeV e - GEANT4 + A´emission

  7. NA64: Setup Key Features of the setup: • High energy beam to trigger the reaction: 100 GeV e- beam from the CERN SPS. • Max intensity ~ 5 x 10 6 e - / spill. • Typically 2 spills/min • Main impurities of H4 beam: π− , low energy e − ( ∼ 1%) μ− and K − ( ≲ 0.1%)

  8. NA64: Setup Key Features of the setup: • High energy beam to trigger the reaction: 100 GeV e- beam from the CERN SPS. • Max intensity ~ 5 x 10 6 e - / spill. • Typically 2 spills/min • Main impurities of H4 beam: π− , low energy e − ( ∼ 1%) μ− and K − ( ≲ 0.1%)

  9. NA64: Setup Key Features of the setup: • High hermeticity: ECAL - PbSc sandwich, 38 × 38 × 445 mm 3 ( ∼ 40 X0) with WLS fiber inserted in spiral ~ 9%/ √ (E[GeV]) energy resolution

  10. NA64: Setup Key Features of the setup: • High hermeticity: 4 HCAL FeSc sandwich modules, 60 × 60 × 150 cm3 ( ∼ 7 λ for each module) with WLS fiber and 60%/ √ (E[GeV] energy resolution.

  11. NA64: Setup Key Features of the setup: • Measure momentum: Tracking system made of 4 MicroMegas modules and 2 GEM detectors together with 2 MPBL magnet ~7 T· m to measure momentum of incoming particles.

  12. NA64: Setup Entries 40000 2 2 / ndf / ndf χ χ 825.9 / 23 825.9 / 23 Constant Constant 3.892e+04 3.892e+04 6.808e+01 6.808e+01 ± ± 35000 Mean Mean 99.97 99.97 0.00 0.00 ± ± Sigma Sigma 1.184 1.184 0.002 0.002 ± ± 30000 25000 20000 Key Features of the setup: 15000 • Measure momentum: 10000 Reconstructed momentum 5000 0 70 80 90 100 110 120 130 140 Energy(GeV) Momentum (GeV)

  13. NA64: Setup 200 Momentum(GeV) Entries Entries 1934 1934 2 10 180 Low energy tail Mean x Mean x 0.001719 0.001719 Mean y Mean y 97.35 97.35 160 to be suppressed Std Dev x Std Dev x 0.00268 0.00268 Std Dev y Std Dev y 5.411 5.411 140 120 10 100 80 60 1 40 20 0 0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 Angle(rad) 200 Momentum(GeV) 30650 30650 Entries Entries 180 0.001004 0.001004 Mean x Mean x Key Features of the setup: Mean y Mean y 100.1 100.1 3 10 160 Std Dev x Std Dev x 0.0008119 0.0008119 Std Dev y Std Dev y 2.386 2.386 • Measure momentum: 140 120 Momentum tracked as a 2 10 100 function of incoming angle 80 60 10 40 20 0 1 0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 Angle(rad)

  14. NA64: Setup Key Features of the setup: • Suppress hadronic background: Synchrotron radiation tagging system (BGO/PbSc sandwich calorimeter) to reject μ− , π− and K − decay in flight after interaction with ECAL.

  15. NA64: Setup Synchrotron radiation Key Features of the setup: • Suppress hadronic background: Synchrotron radiation tagging to reject hadrons at a level of 10 -5 . arXiv: 1703.05993

  16. July’ 2016 Run

  17. July 2016 results No selection cut applied 2.75 x 10 9 electrons on target with beam intensity of 1.4 x 10 6 e - / 4.8 s spill for a ~ 2 cm diameter beam: • Region I —> rare QED dimuon production e - Z → e - Z γ ; γ → µ + µ - , characterised by the energy of ≃ 10 E HCAL GeV GeV deposited by the dimuon pair in the HCAL. • Region II —> SM events from the hadron electroproduction in the target: E ECAL + E HCAL ≃ 100 GeV. • Region III —> few ~ 10 − 2 mostly pile-up of e − and beam hadrons. E ECAL GeV

  18. July 2016 results Event Selection Criteria: • Pile up suppression using timing information. E HCAL GeV • Selecting clean incoming track (angle + single hit in all 4 MMs) with correct momentum. • Hadron suppression with synchrotron radiation. • Events with shower profile as expected. No Signal • No activity in Veto 2. E ECAL GeV Selection cuts applied

  19. July 2016 results • No event observed in the signal box from the July’2016 data. • New limits set on the 𝞭 -A’ mixing strength. arXiV:1610.02988 Phys. Rev. Lett. 118, 011802 (2017)

  20. New BaBar Results arXiv:1702.03327 BABAR Collab Explanation of (g-2) µ with invisible A´ is excluded.

  21. October 2016 run and prospects • October 2016 run : ‣ Good performance at 5x10 6 e-/spill ‣ 4x10 10 eot collected. ‣ Data analysis in progress. 6 1 0 • 2017 run 2 r e ‣ Improved e- tagging: tracker+SRD b o t c ‣ Tests at intensity (7–8)x10 6 e-/spill O ‣ Goal (2–3)x10 11 eot. Projected Sensitivity

  22. Summary The conceptual idea of NA64 is to search for dark sector physics in missing- energy events with an active beam dump experiment. The run 2016: • All detectors performed quite efficiently at high intensity and showed positive results for being able to run at even higher flux. • The July 2016 run set new limits on the 𝞭 -A’ mixing and explanation of the (g-2) µ anomaly with invisible A’ is excluded. • October 2016 data analysis in progress. The run 2017 : • Plan to collect up to few 10 11 electrons on target for the invisible channel and cover significant area of the A’ parameter space. • Upgrades to the tracking system as well as to the synchrotron radiation detectors are foreseen. • We also intend to switch to visible mode to collect few 10 10 eot (> 1 week ) to address the Be8 decay anomaly which could be explained by a 17 MeV boson.

  23. Physics Prospects Process New Physics Sensitivity 1. e - Z -> e - Z + E miss ◇ A ´ -> e + e - Dark Sector: 10 -3 < ε <10 -6 ◇ A ´ -> invisible M A´ ~ sub-GeV Dark Photons and DM ◇ alps New light states (V,S) mQ <10 -5 -10 -7 e ◇ milli-Q weakly coupled to e- M mQ ~ sub-GeV 8 Be excess 2. μ - Z-> μ - Z+ E miss ◇ Z μ -> νν , μ + μ - (g-2) μ anomaly, α μ < 10 -11 -10 -9 ◇ a μ New Z µ from L μ -L τ gauged σ µ τ / σ µ < 10 -9 -10 -8 ◇ μ -> τ conversion symm., scalars coupled to μ LFV 3. π (K)p-> M 0 n + E miss ◇ K L -> invisible CP, CPT symmetry Br <10 -8 -10 -6 , Bell-Steinberger Unitarity, ◇ K S -> invisible Complementary to K- new WC particles: > πνν ◇ π 0 , η , η ´ -> invisible NHL , φφ , VV Br< 10 -8 -10 -7 4. pA -> Z ´ + E miss ◇ leptophobic Z ´ ~ GeV DM σ Z ´ <10 -7 -10 -8 /p

  24. Thank You !!

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