arXiv subjects

Tamas Almos Vami

Publications and source records attributed to Tamas Almos Vami.

11 recordsLinked to original sources

arXiv2026

Feasibility of a collider-based detector search for upward-going fermions produced from gravitationally-bound dark matter within the Earth

Dark matter is theorized to be gravitationally captured within the Earth and to subsequently annihilate into dark photons. The dark photons kinetically mix with the Standard Model photons which would allow the decay of the dark photon to pairs of observable fermions near Earth's surface. We examine the feasibility and sensitivity of an LHC-class general-purpose detector to observe muons originating from these dark matter models. We calculate the expected signal rates at a hypothetical general-purpose detector and examine the effect of significant backgrounds on sensitivity. We also consider experimental efficiencies of such a detector to determine expected limits for the proposed analysis. We find these expected limits constitute a significant improvement over existing ones, strongly motivating a search for upward-going muons stemming from dark matter bound within the Earth.

hep-ph↗

arXiv2025

The Light Dark Matter eXperiment

Searching for dark matter (DM) at colliders is one of the biggest challenges in high-energy physics today. Significant efforts have been made to detect DM within the mass range of 1-10,000 GeV at the Large Hadron Collider and other experiments. However, the lower mass range of 0.001-1 GeV remains largely unexplored, despite strong theoretical motivation from thermal dark matter models in that mass range. The Light Dark Matter eXperiment (LDMX) is a proposed fixed-target experiment at SLAC's LCLS-II 8 GeV electron beamline, specifically designed for the direct production of sub-GeV dark matter. The experiment operates on the principle of detecting missing momentum and missing energy signatures. In this talk, we will present the experimental design of LDMX detector and discuss strategies for detecting dark matter. The talk will detail traditional discriminants-based methods using the electromagnetic and hadronic calorimeters as a veto for Standard Model processes. Additionally, the application of advanced machine learning techniques, such as boosted decision trees and graph neural networks, for distinguishing signal from background will be discussed.

hep-ex↗

arXiv2025

Search for black holes and sphalerons using novel machine learning techniques at CMS

A comprehensive search for microscopic black holes and electroweak sphalerons is presented, using proton-proton collision data collected by the CMS detector during 2016-2018, corresponding to an integrated luminosity of $138~\mathrm{~fb}^{-1}$. A novel tool has been developed to identify collider events with distinct kinematic features, based on the phase-space distance between events. Model-independent limits are set on the cross section of new physics signals producing multiple jets and leptons, which are further interpreted as constraints on black hole and sphaleron production. In the context of models with large extra dimensions, semiclassical black holes with masses below 9.0-11.4 TeV are excluded by this search, significantly extending previous sensitivity. Additionally, a dedicated search for electroweak sphaleron transitions has been performed. An upper limit of 0.0025 is set at 95% confidence level on the fraction of quark-quark interactions with center-of-mass energy above the nominal threshold of 9 TeV that result in sphaleron transitions.

hep-ex↗

arXiv2025

Weakly supervised anomaly detection with event-level variables

We introduce a new topology for weakly supervised anomaly detection searches, di-object plus~X. In this topology, one looks for a resonance decaying to two standard model particles produced in association with other anomalous event activity (X). This additional activity is used for classification. We demonstrate how anomaly detection techniques which have been developed for di-jet searches focusing on jet substructure anomalies can be applied to event-level anomaly detection in this topology. To robustly capture event-level features of multi-particle kinematics, we employ new physically motivated variables derived from the geometric structure of a collision's phase space manifold. As a proof of concept, we explore the application of this approach to several benchmark signals in the di-$τ$ and di-$μ$ plus~X final states. We demonstrate that our anomaly detection approach can reach discovery-level significances for signals that would be missed in a conventional bump-hunt approach.

hep-ph↗

arXiv2024

Search for long-lived charged particles using the CMS detector in Run-2

Long-lived charged particles are predicted by various theories beyond the Standard Model, leading to unique signatures that could reveal new physics. At the LHC, the CMS detector enables searches for these massive particles, identifiable by their characteristic ionization patterns. Using data collected during 2017-2018, we search for signals of anomalous ionization in the silicon tracker. We present a novel approach to background prediction, utilizing the distinct ionization measurements of the silicon pixel and strip detectors as independent variables. We interpret the results within several models including those with staus, stops, gluinos, and multiply charged particles as well as a new model with decays from a Z' boson

hep-ex↗

arXiv2023

Simulated performance and calibration of CMS Phase-2 Upgrade Inner Tracker sensors

The next upgrade of the Large Hadron Collider (LHC) is planned from 2026 when the collider will move to its High Luminosity phase (HL-LHC). The CMS detector needs to be substantially upgraded during this period to exploit the fourfold increase in luminosity provided by the HL-LHC. This upgrade is referred to as the CMS Phase-2 Upgrade. A program of laboratory and beam test measurements, and performance studies based on the detailed simulation of the detector was carried out to support the decision of the technology of the sensors to be adopted in the different regions of the detector for the Phase-2 Upgrade. Among the various options considered, CMS chose to use 3D sensors with a 25 $\times$ 100 $μ$m$^2$ pixel cell in the innermost layer of the barrel and planar sensors with a 25 $\times$ 100 $μ$m$^2$ pixel cell elsewhere. In this paper, we detail the simulation studies that were carried out to choose the best sensor design. These studies include a detailed standalone simulation of the sensors made with PixelAV and the expected performance on high level observables obtained with the simulation and reconstruction software of the CMS experiment.

physics.ins-det↗

arXiv2019

Searches for gluinos and squarks

Despite the great success of the Standard Model, it still does not explain Dark Matter, matter/antimatter asymmetry and it does not unite the electroweak and the strong forces. As a possible solution, the theory of Supersymmetry was proposed. In this paper, three searches for strong production Supersymmetry are presented. The data correspond to a total integrated luminosity of 137 fb$^{-1}$ at a center-of-mass energy of 13 TeV, recorded at the Large Hadron Collider during the years 2015-2018. There has been no significant excess observed relative to the Standard Model predictions. The data gave the following best 95\% exclusion limits for the masses of squarks and gluinos: 2250 GeV, 1260 GeV and 1225 GeV which are obtained from the inclusive search for gluinos, bottom squarks and top squarks, respectively. The search for disappearing tracks extends the gluino mass limit to as much as 2460 GeV, and the neutralino mass limit to as much as 2000 GeV.

hep-ex↗

arXiv2019

Calibration and performance of the CMS pixel detector in LHC Run 2

The Compact Muon Solenoid (CMS) is one of two general-purpose detectors that reconstruct the products of high energy particle interactions at the Large Hadron Collider at CERN. The silicon pixel detector is the innermost component of the CMS tracking system. It determines the trajectories of charged particles originating from the interaction region with high resolution enabling precise momentum and impact parameter measurements in the tracker. It is designed to operate in the high particle density environment of the LHC. The calibration of the pixel detector plays an important role in its performance. The calibration constants follow the physical changes in the sensors that are mostly induced by irradiation. These constants are regularly updated, maintained in a calibration database and used for the event reconstruction. We will present details on the offline calibration procedures and their effects on detector performance during the Run 2 period of LHC.

physics.ins-det↗

arXiv2019

Searches for strong production of supersymmetry in CMS

Searches for production of supersymmetric partners of gluons and quarks with the CMS experiment at CERN's LHC have excluded these particles for masses up to about 2 TeV. The paper will present results and show the analysis techniques in these searches, with an emphasis on the use of razor variables for the discrimination between standard model backgrounds and signal.

hep-ex↗

arXiv2018

Study of the CMS Phase-1 Pixel Pilot Blade Reconstruction

The Compact Muon Solenoid (CMS) detector is one of two general-purpose detectors that measure the products of high energy particle interactions in the Large Hadron Collider (LHC) at CERN. The silicon pixel detector is the innermost component of the CMS tracking system. The detector which was in operation between 2009 and 2016 has now been replaced with an upgraded one in the beginning of 2017. During the previous shutdown period of the LHC, a prototype readout system and a third disk was inserted into the old forward pixel detector with eight prototype blades constructed using the new digital read-out chips. Testing the performance of these pilot modules enabled us to gain operational experience with the upgraded detector. In this paper, the reconstruction and analysis of the data taken with the new modules are presented including information on the calibration of the reconstruction software. The hit finding efficiency and track-hit residual distributions are also shown.

physics.ins-det↗

arXiv2015

Calibration of the CMS Pixel Detector at the Large Hadron Collider

The Compact Muon Solenoid (CMS) detector is one of two general-purpose detectors that reconstruct the products of high energy particle interactions at the Large Hadron Collider (LHC) at CERN. The silicon pixel detector is the innermost component of the CMS tracking system. It determines the trajectories of charged particles originating from the interaction region in three points with high resolution enabling precise momentum and impact parameter measurements in the tracker. The pixel detector is exposed to intense ionizing radiation generated by particle collisions in the LHC. This irradiation could result in temporary or permanent malfunctions of the sensors and could decrease the efficiency of the detector. We have developed procedures in order to correct for these effects. In this paper, we present the types of malfunctions and the offline calibration procedures. We will also show the efficiency and the resolution of the detector in 2012.

physics.ins-det↗