arXiv subjects

I. V. Voronchikhin

Publications and source records attributed to I. V. Voronchikhin.

24 records · Page 2Linked to original sources

arXiv2023

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

In this study, 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 momentum. The analysis was performed using data collected by the NA64-$e$ experiment in 2022. Our study is based on calorimetric measurements, exploiting the different interaction mechanisms of electrons and hadrons in the NA64-ECAL and NA64-HCAL detectors. We determined the intrinsic hadronic contamination by comparing the results obtained using the nominal electron/positron beamline configuration with those obtained in a dedicated setup, in which only hadrons impinged on the detector. The significant differences in the experimental signatures of electrons and hadrons motivated our approach, resulting in a small and well-controlled systematic uncertainty for the measurement. Our study allowed us to precisely determine the intrinsic hadronic contamination, which represents a crucial parameter for the NA64 experiment in which the hadron contaminants may result in non-trivial backgrounds. Moreover, we performed dedicated Monte Carlo simulations for the hadron production induced by the primary T2 target. We found a good agreement between measurements and simulation results, confirming the validity of the applied methodology and our evaluation of the intrinsic hadronic contamination.

hep-ex↗

arXiv2023

Probing Light Dark Matter with positron beams at NA64

We present the results of a missing-energy search for Light Dark Matter which has a new interaction with ordinary matter transmitted by a vector boson, called dark photon $A^\prime$. For the first time, this search is performed with a positron beam by using the significantly enhanced production of $A^\prime$ in the resonant annihilation of positrons with atomic electrons of the target nuclei, followed by the invisible decay of $A^\prime$ into dark matter. No events were found in the signal region with $(10.1 \pm 0.1)~\times~10^{9}$ positrons on target with 100 GeV energy. This allowed us to set new exclusion limits that, relative to the collected statistics, prove the power of this experimental technique. This measurement is a crucial first step toward a future exploration program with positron beams, whose estimated sensitivity is here presented.

hep-ex↗

arXiv2023

Search for Light Dark Matter with NA64 at CERN

Thermal dark matter models with particle $χ$ masses below the electroweak scale can provide an explanation for the observed relic dark matter density. This would imply the existence of a new feeble interaction between the dark and ordinary matter. We report on a new search for the sub-GeV $χ$ production through the interaction mediated by a new vector boson, called the dark photon $A'$, in collisions of 100 GeV electrons with the active target of the NA64 experiment at the CERN SPS. With $9.37\times10^{11}$ electrons on target collected during 2016-2022 runs NA64 probes for the first time the well-motivated region of parameter space of benchmark thermal scalar and fermionic dark matter models. No evidence for dark matter production has been found. This allows us to set the most sensitive limits on the $A'$ couplings to photons for masses $m_{A'} \lesssim 0.35$ GeV, and to exclude scalar and Majorana dark matter with the $χ-A'$ coupling $α_D \leq 0.1$ for masses $0.001 \lesssim m_χ\lesssim 0.1$ GeV and $3m_χ\leq m_{A'}$.

hep-ex↗

arXiv2023

Resonant probing spin-0 and spin-2 dark matter mediators with fixed target experiments

We discuss the mechanism to produce electron-specific dark matter mediators of spin-0 and spin-2 in the electron fixed target experiments such as NA64 and LDMX. The secondary positrons induced by the electromagnetic shower can produce the mediators via annihilation on atomic electrons. That mechanism, for some selected kinematics, results in the enhanced sensitivity with respect to the bounds derived by the bremsstrahlunglike emission of the mediator in the specific parameter space. We derive the corresponding experimental reach of the NA64 and LDMX.

hep-ph↗

arXiv2023

Probing hidden sectors with a muon beam: implication of spin-0 dark matter mediators for muon $(g-2)$ anomaly and 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 $μ^- + N \rightarrow μ^- + N + S(P)$. Their possible subsequent invisible decay into a pair of Dirac DM particles, $S(P) \to χ\overlineχ$, 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 NA64$μ$, MUoNE and M3; in neutrino experiments using powerful proton beams such as DUNE. In particular, we focus on the NA64$μ$ 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 favoured region considering $10^{12}$ and $10^{13}$ muons on target.

hep-ph↗

arXiv2022

Probing hidden spin-2 mediator of dark matter with NA64e, LDMX, NA64$μ$ and M$^3$

The connection between Standard Model (SM) particles and dark matter (DM) can be introduced via hidden spin-2 massive mediator. In the present paper we consider the simplified benchmark link between charged lepton sector of SM and DM particles which are considered to be a hidden Dirac fermions from the dark sector. The regarding couplings are established through the dimension-5 operators involving spin-2 mediator field and the energy-momentum tensors of both SM and DM sectors. We study in detail the implication of this scenario for the lepton fixed-target facilities, such as NA64$e$, LDMX, NA64$μ$ and M$^3$. In particular, for the specific experiment we discuss in detail the missing-energy signatures of spin-2 boson production followed by its invisible decay into stable DM pairs. Moreover, we derive the expected reaches of these experiments for the projected statistics of the leptons accumulated on the target. We also discuss the implication of both nuclear and atomic form-factor parametrizations for the differential spectra of hidden spin-$2$ boson emission, the total cross-section of its production and the experimental reach of the fixed-fixed target facilities for probing hidden spin-$2$ DM mediator.

hep-ph↗