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Priscilla Pani

Publications and source records attributed to Priscilla Pani.

13 recordsLinked to original sources
arXiv2025

MAIA: A new detector concept for a 10 TeV muon collider

Muon colliders offer a compelling opportunity to explore the TeV scale and conduct precision tests of the Standard Model, all within a relatively compact geographical footprint. This paper introduces a new detector concept, MAIA (Muon Accelerator Instrumented Apparatus), optimized for $\sqrt{s}=10$ TeV $\mu^+ \mu^-$ collisions. The detector features an all-silicon tracker immersed in a 5T solenoid field. High-granularity silicon-tungsten and iron-scintillator calorimeters surrounding the solenoid capture high-energy electronic and hadronic showers, respectively, and support particle-flow reconstruction. The outermost subsystem comprises an air-gap muon spectrometer, which contributes to muon identification. The performance of the MAIA detector is evaluated in terms of differential particle reconstruction efficiencies and resolutions. Beam-induced background and incoherent pair production simulations are overlaid to single particle gun samples to assess detector reconstruction capabilities under realistic experimental conditions. Even in the presence of backgrounds, reconstruction efficiencies exceed approximately 95\% for energetic tracks, photons, and charged pions in the central region of the detector. This paper outlines promising avenues for future work, including forward region optimization, opportunities for enhanced flavor tagging and boosted object reconstruction, and technological developments needed to achieve the desired detector performance.

physics.ins-det↗
arXiv2022

Displaying dark matter constraints from colliders with varying simplified model parameters

The search for dark matter is one of the main science drivers of the particle and astroparticle physics communities. Determining the nature of dark matter will require a broad approach, with a range of experiments pursuing different experimental hypotheses. Within this search program, collider experiments provide insights on dark matter which are complementary to direct/indirect detection experiments and to astrophysical evidence. To compare results from a wide variety of experiments, a common theoretical framework is required. The ATLAS and CMS experiments have adopted a set of simplified models which introduce two new particles, a dark matter particle and a mediator, and whose interaction strengths are set by the couplings of the mediator. So far, the presentation of LHC and future hadron collider results has focused on four benchmark scenarios with specific coupling values within these simplified models. In this work, we describe ways to extend those four benchmark scenarios to arbitrary couplings, and release the corresponding code for use in further studies. This will allow for more straightforward comparison of collider searches to accelerator experiments that are sensitive to smaller couplings, such as those for the US Community Study on the Future of Particle Physics (Snowmass 2021), and will give a more complete picture of the coupling dependence of dark matter collider searches when compared to direct and indirect detection searches. By using semi-analytical methods to rescale collider limits, we drastically reduce the computing resources needed relative to traditional approaches based on the generation of additional simulated signal samples.

hep-ph↗
arXiv2022

Leptoquark manoeuvres in the dark: a simultaneous solution of the dark matter problem and the $R_{D^{(*)}}$ anomalies

The measured branching fractions of $B$-mesons into leptonic final states derived by the LHCb collaboration hint towards the breakdown of lepton flavour universality. In this work we take at face value the so-called $R_{D^{(*)}}$ observables that are defined as the ratios of neutral $B$-meson charged-current decays into a charged $D$-meson, a charged lepton and a neutrino final state in the tau and muon channels. A well-studied and simple solution to this charged current anomaly is to introduce a scalar leptoquark $S_1$ that couples to the second and third generation of fermions. We investigate how $S_1$ can also serve as a mediator between the Standard Model and a dark sector. We study this scenario in detail and estimate the constraints arising from collider searches for leptoquarks, collider searches for missing energy signals, direct detection experiments and the dark matter relic abundance. We stress that the production of a pair of leptoquarks that decays into different final states (i.e. the commonly called "mixed" channels) provides critical information for identifying the underlying dynamics, and we exemplify this by studying the $t τb ν$ and the resonant $S_1$ plus missing energy channels. We find that direct detection data provides non-negligible constraints on the leptoquark coupling to the dark sector, which in turn affects the relic abundance. We also show that the correct relic abundance can not only arise via standard freeze-out, but also through conversion-driven freeze-out. We illustrate the rich phenomenology of the model with a few selected benchmark points, providing a broad stroke of the interesting connection between lepton flavour violation and dark matter.

hep-ph↗
arXiv2021

Study of energy response and resolution of the ATLAS Tile Calorimeter to hadrons of energies from 16 to 30 GeV

Three spare modules of the ATLAS Tile Calorimeter were exposed to test beams from the Super Proton Synchrotron accelerator at CERN in 2017. The measurements of the energy response and resolution of the detector to positive pions and kaons and protons with energy in the range 16 to 30 GeV are reported. The results have uncertainties of few percent. They were compared to the predictions of the Geant4-based simulation program used in ATLAS to estimate the response of the detector to proton-proton events at Large Hadron Collider. The determinations obtained using experimental and simulated data agree within the uncertainties.

physics.ins-det↗
arXiv2021

Single-top final states as a probe of top-flavoured dark matter models at the LHC

Models incorporating flavoured dark matter provide an elegant solution to the dark matter problem, evading the tight LHC and direct direction constraints on simple WIMP models. In Dark Minimal Flavour Violation, a simple framework of flavoured dark matter with new sources of flavour violation, the constraints from thermal freeze-out, direct detection experiments, and flavour physics create well-defined benchmark scenarios for these models. We study the LHC phenomenology of four such scenarios, focusing on final states where a single top quark is produced accompanied by no jets, one jet from the fragmentation of light quarks or a $b$-tagged jet. For each of these signatures we develop a realistic LHC analysis, and we show that the proposed analyses would increase the parameter space coverage for the four benchmarks, compared to existing flavour-conserving LHC analyses. Finally we show the projected discovery potential of the considered signatures for the full LHC statistics at 14 TeV, and for the High Luminosity LHC.

hep-ph↗
arXiv2018

LHC Dark Matter Working Group: Next-generation spin-0 dark matter models

Dark matter (DM) simplified models are by now commonly used by the ATLAS and CMS Collaborations to interpret searches for missing transverse energy ($E_T^\mathrm{miss}$). The coherent use of these models sharpened the LHC DM search program, especially in the presentation of its results and their comparison to DM direct-detection (DD) and indirect-detection (ID) experiments. However, the community has been aware of the limitations of the DM simplified models, in particular the lack of theoretical consistency of some of them and their restricted phenomenology leading to the relevance of only a small subset of $E_T^\mathrm{miss}$ signatures. This document from the LHC Dark Matter Working Group identifies an example of a next-generation DM model, called $\textrm{2HDM+a}$, that provides the simplest theoretically consistent extension of the DM pseudoscalar simplified model. A comprehensive study of the phenomenology of the $\textrm{2HDM+a}$ model is presented, including a discussion of the rich and intricate pattern of mono-$X$ signatures and the relevance of other DM as well as non-DM experiments. Based on our discussions, a set of recommended scans are proposed to explore the parameter space of the $\textrm{2HDM+a}$ model through LHC searches. The exclusion limits obtained from the proposed scans can be consistently compared to the constraints on the $\textrm{2HDM+a}$ model that derive from DD, ID and the DM relic density.

hep-ex↗
arXiv2018

DM+$b\bar b$ simulations with DMSimp: an update

Searches for dark matter (DM) produced using collider data probe wide regions of the allowed parameter space of many models and have become competitive with more traditional searches. The interpretations of the results can be efficiently performed in simplified models, which feature only a mediator and a DM candidate together with the interactions among them and the standard model particles. The DMSimp model in FeynRules currently features a wide set of $s$-channel simplified models and can be exploited by the MadGraph5_aMC@NLO framework to produce event samples including NLO QCD corrections for realistic simulations. Higher-order corrections typically have a sizeable impact on the total production rate and lead to a reduction of the theoretical uncertainties. In this short note we report on a recent update of the DMSimp model, which makes it possible to simulate dark matter production in association with bottom quarks in a mixed four-flavour scheme, where the $\overline{\rm MS}$ renormalisation for the bottom-quark Yukawa is employed, while the bottom quark mass is on shell. By comparing with five-flavour scheme, we show that the mixed four-flavor scheme provides reliable predictions for DM+$b\bar b$ final states in a wide range of DM masses.

hep-ex↗
arXiv2018

Flavour-violating decays of mixed top-charm squarks at the LHC

We explore signatures related to squark decays in the framework of non-minimally flavour-violating Supersymmetry. We consider a simplified model where the lightest squark consists of an admixture of charm and top flavour. By recasting the existing LHC searches for top and charm squarks, we show that the limits on squark masses from these analyses are significantly weakened when the top-charm mixing is sizeable. We propose a dedicated search for squarks based on the $tc+{E_{\mathrm{T}}^{\mathrm{miss}}}$ final state which enhances the experimental sensitivity for the case of high mixing, and we map its expected reach for the forthcoming runs of the LHC. We emphasize the role of analyses requiring a jet tagged as produced by the fragmentation of a charm quark in understanding the squark mixing pattern, thus providing a novel handle on new physics. Our results show that, in order to achieve full coverage of the parameter space of supersymmetric models, it is necessary to extend current experimental search programmes with analyses specifically targeting the cases where the lightest top-partner is a mixed state.

hep-ph↗
arXiv2018

Dark matter production in association with a single top-quark at the LHC in a two-Higgs-doublet model with a pseudoscalar mediator

The sensitivity of the LHC experiments to the associated production of dark matter with a single top is studied in the framework of an extension of the standard model featuring two Higgs doublets and an additional pseudoscalar mediator. It is found that the experimental sensitivity is dominated by the on-shell production of a charged Higgs boson, when this assumes a mass below 1 TeV. Dedicated selections considering one and two lepton final states are developed to assess the coverage in parameter space for this signature at a centre-of-mass energy of 14 TeV assuming an integrated luminosity of 300 fb$^{-1}$. For a pseudoscalar mediator with mass 150 GeV and maximally mixed with the pseudoscalar of the two Higgs doublets, values of $tanβ$ up to 3 and down to 15 can be excluded at 95% CL, if the $H^{\pm}$ mass is in the range 300 GeV-1 TeV. This novel signature complements the parameter space coverage of the mono-Higgs, mono-Z and $t{\bar t}$+$E_{\mathrm T}^{\mathrm miss}$ signatures considered in previous publications for this model.

hep-ph↗
arXiv2017

Determining the CP nature of spin-0 mediators in associated production of dark matter and $t \bar t$ pairs

In the framework of spin-0 $s$-channel simplified models, we explore the possibility of assessing the structure of dark matter interactions through the associate production of dark matter and $t\bar{t}$ pairs. To this purpose, final states with two leptons are considered and the kinematic properties of the dilepton system is studied. We develop a realistic analysis strategy and provide a detailed evaluation of the achievable sensitivity for the dark matter signal assuming integrated luminosities of $300 \, {\rm fb}^{-1}$ and $3 \, {\rm ab}^{-1}$ at the 14 TeV LHC. Furthermore, upper limits on the mediator masses for which the two different CP hypotheses can be distinguished are derived. The obtained limits on the signal strengths are finally translated into constraints on the parameter space of two spin-0 simplified models including a scenario with an extended Higgs sector.

hep-ph↗
arXiv2016

Simplified Models for Dark Matter Searches at the LHC

This document outlines a set of simplified models for dark matter and its interactions with Standard Model particles. It is intended to summarize the main characteristics that these simplified models have when applied to dark matter searches at the LHC, and to provide a number of useful expressions for reference. The list of models includes both s-channel and t-channel scenarios. For s-channel, spin-0 and spin-1 mediation is discussed, and also realizations where the Higgs particle provides a portal between the dark and visible sectors. The guiding principles underpinning the proposed simplified models are spelled out, and some suggestions for implementation are presented.

hep-ph↗
arXiv2015

Dark Matter Benchmark Models for Early LHC Run-2 Searches: Report of the ATLAS/CMS Dark Matter Forum

This document is the final report of the ATLAS-CMS Dark Matter Forum, a forum organized by the ATLAS and CMS collaborations with the participation of experts on theories of Dark Matter, to select a minimal basis set of dark matter simplified models that should support the design of the early LHC Run-2 searches. A prioritized, compact set of benchmark models is proposed, accompanied by studies of the parameter space of these models and a repository of generator implementations. This report also addresses how to apply the Effective Field Theory formalism for collider searches and present the results of such interpretations.

hep-ex↗