4 research outputs found
Constraining light thermal inelastic dark matter with NA64
A vector portal between the Standard Model and the dark sector is a predictive and compelling framework for thermal dark matter. Through co-annihilations, models of inelastic dark matter (iDM) and inelastic Dirac dark matter (i2DM) can reproduce the observed relic density in the MeV to GeV mass range without violating cosmological limits. In these scenarios, the vector mediator behaves like a semi-visible particle, evading traditional bounds on visible or invisible resonances, and uncovering new parameter space to explain the muon anomaly. By means of a more inclusive signal definition at the NA64 experiment, we place new constraints on iDM and i2DM using a missing energy technique. With a recast-based analysis, we contextualize the NA64 exclusion limits in parameter space and estimate the reach of the newly collected and expected future NA64 data. Our results motivate the development of an optimized search program for semi-visible particles, in which fixed-target experiments like NA64 provide a powerful probe in the sub-GeV mass range
Measurement of the intrinsic hadronic contamination in the NA64âe high-purity eâş/eâť 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
Search for a light ZⲠin the LÎź-LĎ scenario with the NA64-e experiment at CERN
The extension of Standard Model made by inclusion of additional U(1) gauge LÎź-LĎ symmetry can explain the difference between the measured and the predicted value of the muon magnetic moment and solve the tension in B meson decays. This model predicts the existence of a new, light ZⲠvector boson, predominantly coupled to second and third generation leptons, whose interaction with electrons is due to a loop mechanism involving muons and taus. In this work, we present a rigorous evaluation of the upper limits in the ZⲠparameter space, obtained from the analysis of the data collected by the NA64-e experiment at CERN SPS, that performed a search for light dark matter with 2.84Ă1011 electrons impinging with 100 GeV on an active thick target. The resulting limits touch the muon g-2 preferred band for values of the ZⲠmass of order of 1 MeV, while the sensitivity projections for the future high-statistics NA64-e runs demonstrate the power of the electrons/positron beam approach in this theoretical scenario.ISSN:1550-7998ISSN:0556-2821ISSN:1550-236
Search for a New B-L ZⲠGauge Boson with the NA64 Experiment at CERN
A search for a new ZⲠgauge 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 3.22Ă1011 electrons on target collected during 2016-2021 runs, no signal events were found. This allows us to derive new constraints on the Zâ˛-e coupling strength, which, for the mass range 0.3mZⲠ100 MeV, are more stringent compared to those obtained from the neutrino-electron scattering data.ISSN:0031-9007ISSN:1079-711