arXiv subjects

Andrea Tesi

Publications and source records attributed to Andrea Tesi.

At least 37 records · Page 2Linked to original sources

arXiv2023

The Thick Gas Electron Multiplier and its derivatives: physics, technologies and applications

The Thick Gas Electron Multiplier (THGEM) is a robust high-gain gas-avalanche electron multiplier - a building block of a variety of radiation detectors. It can be manufactured economically by standard printed-circuit drilling and etching technology. We present a detailed review of the THGEM and its derivatives. We focus on the physics phenomena that govern their operation and performances under different operation conditions. Technological aspects associated with the production of these detectors and their current and potential applications are discussed.

physics.ins-det↗

arXiv2023

Diamond-like carbon coatings for cryogenic operation of particle detectors

Characterization of diamond-like carbon (DLC) coatings at cryogenic temperatures (down to 77 K) is presented, covering the electrical resistivity range of practical interest to gaseous and liquid particle instrumentation: 10^-1-10^5 Mohm/sq. The good behaviour observed in terms of linearity, surface uniformity and stability with time and transported charge add to other well-known characteristics like low chemical reactivity and tolerance to radiation. The observed temperature dependence and stability of electrical properties with transported charge is consistent with a conductivity mechanism based on 2-dimensional variable-range electron hopping, as expected for the surface conductivity of thin films made from amorphous carbon. First results from a resistive-protected WELL detector ('RWELL') built with DLC and operated close to the liquid-vapor coexistence point of argon (87.5 K at 1 bar) are presented.

physics.ins-det↗

arXiv2022

Test-Beam and Simulation Studies Towards RPWELL-based DHCAL

Digital Hadronic Calorimeters (DHCAL) were suggested for future Colliders as part of the particle-flow concept. Though studied mainly with Resistive Plate Chambers (RPC), studies focusing on Micro-Pattern Gaseous Detector (MPGD)-based sampling elements have shown the potential advantages; they can be operated with environmental friendly gases and reach similar detection efficiency at lower average pad-multiplicity. We summarize here the experimental test-beam results of a small-size DHCAL prototype, incorporating six Micromegas (MM) and two Resistive-Plate WELL (RPWELL) sampling elements, interlaced with steel-absorber plates. It was investigated with 2-6 GeV pion beam at the CERN/PS beam facility. The data permitted validating a GEANT4 simulation framework of a DHCAL, and evaluating the expected pion energy resolution of a full-scale RPWELL-based calorimeter. The pion energy resolution of $\fracσ{E[GeV]}=\frac{50.8\%}{\sqrt{E[GeV]}} \oplus 10.3\%$ derived expected with the RPWELL concept is competitive to that of glass RPC and MM sampling techniques.

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arXiv2022

Dark matter self-interactions in the matter power spectrum

We study the imprints of secluded dark sectors with a mass gap and self-interactions on the matter power spectrum. When Dark Matter (DM) is sufficiently light, in the ballpark of a few KeV, and self-interacting we find qualitative difference with respect to $Λ$CDM and also to free streaming DM. In order to emphasize the role of interactions for the evolution of the primordial perturbations we discuss various regimes: ranging from the ideal case of a tightly coupled perfect fluid to the free case of Warm Dark Matter, including the realistic case of small but non-vanishing self-interactions. We compute the matter power spectrum in all these regimes with the aid of Boltzmann solvers. Light dark sectors with self-interactions are efficiently constrained by Lyman-$α$ data and we find that the presence of self-interactions relaxes the bound on the DM mass. As a concrete realization we study models with dark QCD-like sectors, where DM is made of light dark-pions.

hep-ph↗

arXiv2022

Dark Photon Dark Matter without Stueckelberg Mass

We study the scenario of dark photon Dark Matter where the mass is generated through the Higgs mechanism rather than the constant Stueckelberg mass. In this construction the dark sector contains necessarily extra degrees of freedom and interactions that lead to non-trivial dynamics including thermalization, phase transitions, cosmic string production. As a consequence the predictions of Stueckelberg theories are vastly modified, strongly depending on the couplings to curvature and on the scale of inflation $H_I$ compared to the scale $f$ of spontaneous symmetry breaking. We find in particular that only in extreme regions of parameter space the phenomenology of Stueckelberg dark photon is reproduced. These scenarios are strongly constrained by isocurvature perturbations unless the dark sector is approximately Weyl invariant.

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arXiv2021

Dark QCD Matters

We investigate the nightmare scenario of dark sectors that are made of non-abelian gauge theories with fermions, gravitationally coupled to the Standard Model (SM). While testing these scenarios is experimentally challenging, they are strongly motivated by the accidental stability of dark baryons and pions, that explain the cosmological stability of dark matter (DM). We study the production of these sectors which are minimally populated through gravitational freeze-in, leading to a dark sector temperature much lower than the SM, or through inflaton decay, or renormalizable interactions producing warmer DM. Despite having only gravitational couplings with the SM these scenarios turn out to be rather predictive depending roughly on three parameters: the dark sector temperature, the confinement scale and the dark pion mass. In particular, when the initial temperature is comparable to the SM one these scenarios are very constrained by structure formation, $ΔN_{\rm eff}$ and limits on DM self-interactions. Dark sectors with same temperature or warmer than SM are typically excluded.

hep-ph↗

arXiv2021

General Freeze-in and Freeze-out

We use the framework of relativistic and non-relativistic conformal field theories (CFT) to derive general results relevant for the production of weakly coupled and strongly coupled dark sectors through thermal interactions. Our result reproduce trivially known formulas for $2\to n $ processes and extend to general $m\to n$ processes as well as interacting dark sectors. As concrete examples we consider freeze-in of a relativistic CFT coupled to the SM with contact interactions and derive Sommerfeld enhancement of non-relativistic cross-sections from the theory of fermions at unitarity.

hep-ph↗

arXiv2021

Single Electron Spectra in RPWELL-based detectors

Single-electron avalanche distributions in gaseous multipliers affect their efficient detection and that of single UV-photons. In this work, we investigated the shape of single-photo-electron spectra in single- and double-stage Resistive Plate WELL (RPWELL) detector configurations, operated in $\mathrm{Ne/CH_{4}}$ and $\mathrm{Ar/CH_{4}}$. Discharge-free operation was reached over a broad dynamic range, with charge gains of \numrange[range-phrase = -]{e4}{e6}. Compared to the usual exponential ones, the observed Polya-like charge spectra pave the way towards higher single-electrons detection efficiencies. The latter were evaluated here, using experimental data combined with numerical simulations. The effects of the gas mixtures, electric field configuration and detector geometry on the Polya spectra and their related "$θ$" parameter are presented.

physics.ins-det↗

arXiv2021

The Muon Smasher's Guide

We lay out a comprehensive physics case for a future high-energy muon collider, exploring a range of collision energies (from 1 to 100 TeV) and luminosities. We highlight the advantages of such a collider over proposed alternatives. We show how one can leverage both the point-like nature of the muons themselves as well as the cloud of electroweak radiation that surrounds the beam to blur the dichotomy between energy and precision in the search for new physics. The physics case is buttressed by a range of studies with applications to electroweak symmetry breaking, dark matter, and the naturalness of the weak scale. Furthermore, we make sharp connections with complementary experiments that are probing new physics effects using electric dipole moments, flavor violation, and gravitational waves. An extensive appendix provides cross section predictions as a function of the center-of-mass energy for many canonical simplified models.

hep-ph↗

arXiv2021

Gravitational Production of a Conformal Dark Sector

Dark sectors with purely gravitational couplings to the Standard Model are unavoidably populated from the SM plasma by graviton exchange, and naturally provide DM candidates. We examine the production in the relativistic regime where the dark sector is approximately scale invariant, providing general analytical formulas that depend solely on the central charge of the dark sector. We then assess the relevance of interactions that can lead to a variety of phenomena including thermalisation, nonperturbative mass gaps, out-of-equilibrium phase transitions and cannibalism in the dark sector. As an illustrative example we consider the dark glueball scenario in this light and show it to be a viable DM candidate due to the suppression of gravitational production. We go on to extend these results to strongly coupled CFTs and their holographic duals at large-N with the dark dilaton as the DM candidate.

hep-ph↗

arXiv2021

Dark Nucleosynthesis: Cross-sections and Astrophysical Signals

We investigate dark matter bound-state formation and its implication for indirect-detection experiments. We focus on the case where dark matter is a baryon of a strongly-coupled dark sector and provide generic formulae for the formation of shallow nuclear bound states on emission of photons, and W and Z gauge bosons. These processes can occur via electric and magnetic transitions, and give rise to indirect signals that are testable in monochromatic and diffuse photon measurements by Fermi and HESS. We also study the validity of factorizing the bound-state formation cross section into a short-distance nuclear part multiplied by Sommerfeld-enhancement factors. We find that the short-distance nuclear potential often violates factorization, modifying in particular the location of the peaks associated with zero-energy bound states. Finally we revisit bound-state formation of a (weakly-coupled) Minimal DM quintuplet including isospin-breaking effects, and find it gives rise to indirect-detection signals that are compatible with current bounds.

hep-ph↗

arXiv2020

Indirect Detection of Composite (Asymmetric) Dark Matter

Dark Matter can form bound states upon the emission of quanta of energy equal to the binding energy. The rate of this process is large for strongly-interacting Dark Matter, and further enhanced by long distance effects. The resulting monochromatic and diffuse $γ$-rays can be tested in indirect detection experiments. If Dark Matter has electroweak charge, indirect signals include multiple observable photon lines for masses in the TeV range. Else if it couples only via a dark photon portal, diffuse spectra from dwarf galaxies and CMB reionization set powerful limits for masses below a TeV. This mechanism provides a powerful means of probing Asymmetric Dark Matter today.

hep-ph↗

arXiv2020

Gravitational Waves from Supercool Axions

We study the dynamics of the Peccei-Quinn (PQ) phase transition for the QCD axion. In weakly coupled models the transition is typically second order except in the region of parameters where the PQ symmetry is broken through the Coleman-Weinberg mechanism. In strongly coupled realizations the transition is often first order. We show examples where the phase transition leads to strong supercooling lowering the nucleation temperature and enhancing the stochastic gravitational wave signals. The models predict a frequency peak in the range 100-1000 Hz with an amplitude that is already within the sensitivity of LIGO and can be thoroughly tested with future gravitational wave interferometers.

hep-ph↗

arXiv2019

First demonstration of a bubble-assisted Liquid Hole Multiplier operation in liquid argon

We demonstrate, for the time, the operation of a bubble-assisted Liquid Hole Multiplier (LHM) in liquid argon. The LHM, sensitive to both radiation-induced ionization electrons and primary scintillation photons, consists of a perforated electrode immersed in the noble liquid, with a stable gas-bubble trapped underneath. Electrons deposited in the liquid or scintillation-induced photoelectrons emitted from a photocathode on the electrode's surface, are collected into the holes; after crossing the liquid-gas interface, they induce electroluminescence within the bubble. After having validated in previous works the LHM concept in liquid xenon, we provide here first preliminary results on its operation in liquid argon. We demonstrate the bubble containment under a Thick Gas Electron Multiplier (THGEM) electrode and provide detector response to alpha particles, recorded with a SiPM - under electroluminescence and with modest gas multiplication; the imaging capability is also demonstrated.

physics.ins-det↗

arXiv2018

Cosmological Production of Dark Nuclei

We study the formation of Dark Matter nuclei in scenarios where DM particles are baryons of a new confining gauge force. The dark nucleosynthesis is analogous to the formation of light elements in the SM and requires as a first step the formation of dark deuterium. We compute this process from first principles, using the formalism of pion-less effective theory for nucleon-nucleon interactions. This controlled effective field theory expansion allows us to systematically compute the cross sections for generic SM representations under the assumption of shallow bound states. In the context of vector-like confinement models we find that, for nucleon masses in the TeV range, baryonic DM made of electro-weak constituents can form a significant fraction of dark deuterium and a much smaller fraction of dark tritium. Formation of dark nuclei can also lead to monochromatic photon lines in indirect detection. Models with singlets do not undergo nucleosynthesis unless a dark photon is added to the theory.

hep-ph↗

arXiv2018

Fusing Vectors into Scalars at High Energy Lepton Colliders

We study vector boson fusion production of new scalar singlets at high energy lepton colliders. We find that CLIC has the potential to test single production cross-sections of a few tens of attobarns in di-Higgs and di-boson final states. In models with a sizeable singlet-Higgs mixing, these values correspond to a precision in Higgs couplings of order 0.1% or better. We compare our sensitivities with those of the LHC and interpret our results in well-motivated models like the Twin Higgs, the NMSSM and axion-like particles. Looking forward to even higher energy machines, we show that the reach of muon colliders like LEMMA or MAP overcomes the one of future hadron machines like FCC-hh. We finally study the pair production of the new scalar singlets via an off-shell Higgs. This process does not vanish for small mixings and will constitute a crucial probe of models generating a first order electro-weak phase transition.

hep-ph↗

arXiv2018

An almost elementary Higgs: Theory and Practice

We study models that interpolate between an elementary and a composite Higgs boson. Such models, arising in theories with new vector-like fermions with electro-weak quantum numbers and charged under a confining gauge interaction, are entirely compatible with current data, with only weak bounds from flavor, CP-violation and precision tests. After classifying the models from the point of view of symmetries, we study their collider phenomenology at LHC. In the most relevant scenarios, bounds from present searches exclude heavy scalar isospin triplets and quintuplets up to $\sim 200\;$GeV and we show how dedicated searches of simple signals such as $pp\to 3 γW$ could improve the reach by at least a factor of 2 with present data, reaching $O(1\;{\rm TeV})$ with higher integrated luminosities. States that mix with the SM Higgs can be tested in a variety of final states, such as $2b2γ$ searches relevant for double Higgs production.

hep-ph↗

arXiv2017

B-decay anomalies in Pati-Salam SU(4)

Attempts to incorporate in a coherent picture the $B$-decay anomalies presumably observed in $b\rightarrow c$ and $b\rightarrow s$ semi-leptonic decays have to face the absence of signals in other related experiments, both at low and at high energies. By extending and making more precise the content of Ref. [1], we describe one such attempt based on the Pati-Salam SU(4) group, that unifies colour and the $B$-$L$ charge, in the context of a new strongly interacting sector, equally responsible for producing a pseudo-Goldstone Higgs boson.

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