Probing invisible vector meson decay mode with hadronic beam in the NA64 experiment at SPS/CERN

We test a novel idea of using a $\pi^-$ beam in the fixed-target experiments to search for New Physics in the events with missing energy. Bounds for invisible vector $\rho$ meson decay were derived, analyzed, and compared with the current limits on searching Dark Matter in the accelerator based experiments. We demonstrate that the new approach can be effective tool to probe sub-GeV Dark Matter parameter space.Comment: 8 pages,, 5 figures and 1 Tabl

Dark sectors 2016 Workshop: community report

This report, based on the Dark Sectors workshop at SLAC in April 2016, summarizes the scientific importance of searches for dark sector dark matter and forces at masses beneath the weak-scale, the status of this broad international field, the important milestones motivating future exploration, and promising experimental opportunities to reach these milestones over the next 5-10 years

Energy Resolution Performance of the CMS Electromagnetic Calorimeter

The energy resolution performance of the CMS lead tungstate crystal electromagnetic calorimeter is presented. Measurements were made with an electron beam using a fully equipped supermodule of the calorimeter barrel. Results are given both for electrons incident on the centre of crystals and for electrons distributed uniformly over the calorimeter surface. The electron energy is reconstructed in matrices of 3 times 3 or 5 times 5 crystals centred on the crystal containing the maximum energy. Corrections for variations in the shower containment are applied in the case of uniform incidence. The resolution measured is consistent with the design goals

Probing hidden sectors with a muon beam: Implication of spin-0 dark matter mediators for the muon (g-2) anomaly and the validity of the Weiszäcker-Williams approach

In addition to vector (V) type new particles extensively discussed previously, both CP-even (S) and CP-odd (P) spin-0 dark matter (DM) mediators can couple to muons and be produced in the bremsstrahlung reaction μ-+N→μ-+N+S(P). Their possible subsequent invisible decay into a pair of Dirac DM particles, S(P)→χχ¯, can be detected in fixed target experiments through missing energy signature. In this paper, we focus on the case of experiments using high-energy muon beams. For this reason, we derive the differential cross sections involved using the phase space Weiszäcker-Williams approximation and compare them to the exact-tree-level calculations. The formalism derived can be applied in various experiments that could observe muon-spin-0 DM interactions. This can happen in present and future proton beam-dump experiments such as NA62, SHIP, HIKE, and SHADOWS; in muon fixed target experiments as NA64μ, MUonE and M3; in neutrino experiments using powerful proton beams such as DUNE. In particular, we focus on the NA64μ experiment case, which uses a 160 GeV muon beam at the CERN Super Proton Synchrotron accelerator. We compute the derived cross sections, the resulting signal yields and we discuss the experiment projected sensitivity to probe the relic DM parameter space and the (g-2)μ anomaly favored region considering 1011 and 1013 muons on target.ISSN:1550-7998ISSN:0556-2821ISSN:1550-236

Search for pseudoscalar bosons decaying into e+e- pairs in the NA64 experiment at the CERN SPS

We report the results of a search for a light pseudoscalar particle a that couples to electrons and decays to e+e- performed using the high-energy CERN SPS H4 electron beam. If such light pseudoscalar exists, it could explain the ATOMKI anomaly (an excess of e+e- pairs in the nuclear transitions of Be8 and He4 nuclei at the invariant mass ≃17 MeV observed by the experiment at the 5 MV Van de Graaff accelerator at ATOMKI, Hungary). We used the NA64 data collected in the "visible mode"configuration with a total statistics corresponding to 8.4×1010 electrons on target (EOT) in 2017 and 2018. In order to increase sensitivity to small coupling parameter ϵ we also used the data collected in 2016-2018 in the "invisible mode"configuration of NA64 with a total statistics corresponding to 2.84×1011 EOT. The background and efficiency estimates for these two configurations were retained from our previous analyses searching for light vector bosons and axionlike particles (ALP) (the latter were assumed to couple predominantly to γ). In this work we recalculate the signal yields, which are different due to different cross section and lifetime of a pseudoscalar particle a, and perform a new statistical analysis. As a result, the region of the two dimensional parameter space ma-ϵ in the mass range from 1 to 17.1 MeV is excluded. At the mass of the central value of the ATOMKI anomaly (the first result obtained on the beryllium nucleus, 16.7 MeV) the values of ϵ in the range 2.1×10-4<ϵ<3.2×10-4 are excluded.ISSN:1550-7998ISSN:0556-2821ISSN:1550-236

On Search for eV Hidden Sector Photons in Super-Kamiokande and CAST Experiments.

If light hidden sector photons exist, they could be produced through kinetic mixing with solar photons in the eV energy range. We propose to search for this hypothetical hidden photon flux with the Super-Kamiokande and/or upgraded CAST detectors. The proposed experiments are sensitive to mixing strengths as small as 10^-9 for hidden photon masses in the sub eV region and, in the case of non-observation, would improve limits recently obtained from photon regeneration laser experiments in this mass region.Comment: 12 pages, 3 figure

Search for a New B-L Z′ Gauge Boson with the NA64 Experiment at CERN

A search for a new Z′ gauge boson associated with (un)broken B-L symmetry in the keV-GeV mass range is carried out for the first time using the missing-energy technique in the NA64 experiment at the CERN SPS. From the analysis of the data with 3.22×1011 electrons on target collected during 2016-2021 runs, no signal events were found. This allows us to derive new constraints on the Z′-e coupling strength, which, for the mass range 0.3mZ′ 100 MeV, are more stringent compared to those obtained from the neutrino-electron scattering data.ISSN:0031-9007ISSN:1079-711

Measurement of the intrinsic hadronic contamination in the NA64−e high-purity e⁺/e⁻ beam at CERN

We present the measurement of the intrinsic hadronic contamination at the CERN SPS H4 beamline configured to transport electrons and positrons at 100 GeV/c. The analysis, performed using data collected by the NA64-e experiment in 2022, is based on calorimetric measurements, exploiting the different interaction mechanisms of electrons and hadrons in the NA64 detector. We determined the contamination by comparing the results obtained using the nominal electron/positron beamline configuration with those from a dedicated setup, in which only hadrons impinged on the detector. We also obtained an estimate of the relative protons, anti-protons and pions yield by exploiting the different absorption probabilities of these particles in matter. We cross-checked our results with a dedicated Monte Carlo simulation for the hadron production at the primary T2 target, finding a good agreement with the experimental measurements.ISSN:0168-9002ISSN:1872-957

Performance of Multiplexed XY Resistive Micromegas detectors in a high intensity beam

We present the performance of multiplexed XY resistive Micromegas detectors tested in the CERN SPS 100 GeV/c electron beam at intensities up to 3.3 × 10 5e−/(s-cm2). So far, all studies with multiplexed Micromegas have only been reported for tests with radioactive sources and cosmic rays. The use of multiplexed modules in high intensity environments was not explored due to the effect of ambiguities in the reconstruction of the hit point caused by the multiplexing feature. For the specific mapping and beam intensities analyzed in this work with a multiplexing factor of five, more than 50% level of ambiguity is introduced due to particle pile-up as well as fake clusters due to the mapping feature. Our results prove that by using the additional information of cluster size and integrated charge from the signal clusters induced on the XY strips, the ambiguities can be reduced to a level below 2%. The tested detectors are used in the CERN NA64 experiment for tracking the incoming particles bending in a magnetic field in order to reconstruct their momentum. The average hit detection efficiency of each module was found to be 96% at the highest beam intensities. By using four modules a tracking resolution of 1.1% was obtained with 85% combined tracking efficiency.ISSN:0168-9002ISSN:1872-957