A
bstract
The inclusion of an additional U(1) gauge
L
μ
−
L
τ
symmetry would release the tension between the measured and the predicted value of the anomalous muon magnetic moment: this paradigm ...assumes the existence of a new, light
Z
′ vector boson, with dominant coupling to
μ
and
τ
leptons and interacting with electrons via a loop mechanism. The
L
μ
−
L
τ
model can also explain the Dark Matter relic abundance, by assuming that the
Z
′ boson acts as a “portal” to a new Dark Sector of particles in Nature, not charged under known interactions. In this work we present the results of the
Z
′ search performed by the NA64-
e
experiment at CERN SPS, that collected ~ 9 × 10
11
100 GeV electrons impinging on an active thick target. Despite the suppressed
Z
′ production yield with an electron beam, NA64-
e
provides the first accelerator-based results excluding the
g −
2 preferred band of the
Z
′ parameter space in the 1 keV
<
m
Z
′
≲ 2 MeV range, in complementarity with the limits recently obtained by the NA64-
μ
experiment with a muon beam.
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.
Search for chameleons with CAST Anastassopoulos, V.; Arik, M.; Aune, S. ...
Physics letters. B,
10/2015, Letnik:
749, Številka:
C
Journal Article
Recenzirano
Odprti dostop
In this work we present a search for (solar) chameleons with the CERN Axion Solar Telescope (CAST). This novel experimental technique, in the field of dark energy research, exploits both the ...chameleon coupling to matter (βm) and to photons (βγ) via the Primakoff effect. By reducing the X-ray detection energy threshold used for axions from 1 keV to 400 eV CAST became sensitive to the converted solar chameleon spectrum which peaks around 600 eV. Even though we have not observed any excess above background, we can provide a 95% C.L. limit for the coupling strength of chameleons to photons of βγ≲1011 for 1<βm<106.
The T-REX project aims at developing novel readout techniques for Time Projection Chambers in experiments searching for rare events. The enhanced performance of the latest Micromegas readouts in ...issues like energy resolution, gain stability, homogeneity, material budget, combined with low background techniques, is opening new windows of opportunity for their application in this field. Here we review the latest results regarding the use and prospects of Micromegas readouts in axion physics (CAST and the future helioscope), as well as the R&D carried out within NEXT, to search for the neutrinoless double-beta decay.
The latest generation of Micromegas detectors show a good energy resolution, spatial resolution and low threshold, which make them idoneous in low energy applications. Two micromegas detectors have ...been built for dark matter experiments: CAST, which uses a dipole magnet to convert axion into detectable x-ray photons, and MIMAC, which aims to reconstruct the tracks of low energy nuclear recoils in a mixture of CF4 and CHF3. These readouts have been respectively built with the microbulk and bulk techniques, which show different gain, electron transmission and energy resolutions. The detectors and the operation conditions will be described in detail as well as their discrimination capabilities for low energy photons will be discussed.
Micromegas detectors, thanks to their good spatial and temporal discrimination capabilities, are good candidates for rare event search experiments. Recent X-ray background levels achieved by these ...detectors in the CAST experiment have motivated further studies in the nature of the background levels measured. In particular, different shielding configurations have been tested at the Canfranc Underground Laboratory, using a microbulk type detector which was previously running at the CAST experiment. The first results underground show that this technology, which is made of low radiative materials, is able to reach background levels down to 2 × 10-7 keV-1 s-1 cm-2 with a proper shielding. Moreover, the experimental background measurements are complemented with Geant4 simulations which allow to understand the origin of the background, and to optimize future shielding set-ups.
During the last taking data campaigns of the CAST experiment, the micromegas detectors have achieved background levels about 5 to 9 ×10−6keV−1cm−2s−1 between 2 and 9 keV. This performance has been ...possible thanks to the introduction of the microbulk technology, the implementation of a shielding and the development of discrimination algorithms. It has motivated new studies towards a deeper understanding of CAST detectors background. One of the working lines includes the construction of a replica of the set-up used in CAST by micromegas detectors and its installation in the Canfranc Underground Laboratory. Different contributions to the detectors background have been evaluated and an upper limit < 2 × 10−7keV−1cm−2s−1 for the intrinsic background of the detector has been obtained.
Three experiments investigated the effect of consensus information on majority and minority influence. Experiment 1 examined the effect of consensus expressed by descriptive adjectives (large vs. ...small) on social influence. A large source resulted in more influence than a small source, irrespective of source status (majority vs. minority). Experiment 2 showed that large sources affected attitudes heuristically, whereas only a small minority instigated systematic processing of the message. Experiment 3 manipulated the type of consensus information, either in terms of descriptive adjectives (large, small) or percentages (82%, 18%, 52%, 48%). When consensus was expressed in terms of descriptive adjectives, the findings of Experiments 1 and 2 were replicated (large sources were more influential than small sources), but when consensus was expressed in terms of percentages, the majority was more influential than the minority, irrespective of group consensus.
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