arXiv subjects

Adrian Bevan

Publications and source records attributed to Adrian Bevan.

13 recordsLinked to original sources

arXiv2025

Large area curved silicon modules for future trackers

For many years there has been an aspiration within the community to develop curved silicon detectors for particle physics applications. We present the results from 10 x 10cm low mass support modules as a part of the "ZeroMass" project that aims to minimise the material budget for tracking and vertexing systems for future colliders. We use 50 {\mu}m thick DC coupled strip sensors from Micron Semiconductor Ltd., with a carbon composite support frame. Our current module demonstrators use a radius of curvature of 15cm, typical of that used for the outer parts of large pixel systems, or the inner part of strip trackers and the outer part of large radii vertex detectors. The material budget obtained varies from an $X_0$ of 0.05\% in the active area to 0.62\% in the support structure, with an average of 0.28\%. There is further scope for material budget reduction in applying the concept and methods to large instruments for future detector systems, which we also discuss.

physics.ins-det↗

arXiv2019

HIPSTER -- A python package for particle physics analyses

HIPSTER (Heavily Ionising Particle Standard Toolkit for Event Recognition) is an open source Python package designed to facilitate the use of TensorFlow in a high energy physics analysis context. The core functionality of the software is presented, with images from the MoEDAL experiment Nuclear Track Detectors (NTDs) serving as an example dataset. Convolutional neural networks are selected as the classification algorithm for this dataset and the process of training a variety of models with different hyper-parameters is detailed. Next the results are shown for the MoEDAL problem demonstrating the rich information output by HIPSTER that enables the user to probe the performance of their model in detail.

hep-ex↗

arXiv2019

Machine Learning in High Energy Physics Community White Paper

Machine learning has been applied to several problems in particle physics research, beginning with applications to high-level physics analysis in the 1990s and 2000s, followed by an explosion of applications in particle and event identification and reconstruction in the 2010s. In this document we discuss promising future research and development areas for machine learning in particle physics. We detail a roadmap for their implementation, software and hardware resource requirements, collaborative initiatives with the data science community, academia and industry, and training the particle physics community in data science. The main objective of the document is to connect and motivate these areas of research and development with the physics drivers of the High-Luminosity Large Hadron Collider and future neutrino experiments and identify the resource needs for their implementation. Additionally we identify areas where collaboration with external communities will be of great benefit.

physics.comp-ph↗

arXiv2017

Unitarity Triangle Analysis in the Standard Model and Beyond

Flavour physics represents a unique test bench for the Standard Model (SM). New analyses performed at the LHC experiments are now providing unprecedented insights into CKM metrology and new evidences for rare decays. The CKM picture can provide very precise SM predictions through global analyses. We present here the results of the latest global SM analysis performed by the UTfit collaboration including all the most updated inputs from experiments, lattice QCD and phenomenological calculations. In addition, the Unitarity Triangle (UT) analysis can be used to constrain the parameter space in possible new physics (NP) scenarios. We update here also the UT analysis beyond the SM by the UTfit collaboration. All of the available experimental and theoretical information on $ΔF=2$ processes is reinterpreted including a model-independent NP parametrisation. We determine the allowed NP contributions in the kaon, $D$, $B_d$, and $B_s$ sectors and, in various NP scenarios, we translate them into bounds for the NP scale as a function of NP couplings.

hep-ph↗

arXiv2017

Support Vector Machines and generalisation in HEP

We review the concept of Support Vector Machines (SVMs) and discuss examples of their use in a number of scenarios. Several SVM implementations have been used in HEP and we exemplify this algorithm using the Toolkit for Multivariate Analysis (TMVA) implementation. We discuss examples relevant to HEP including background suppression for $H\toτ^+τ^-$ at the LHC with several different kernel functions. Performance benchmarking leads to the issue of generalisation of hyper-parameter selection. The avoidance of fine tuning (over training or over fitting) in MVA hyper-parameter optimisation, i.e. the ability to ensure generalised performance of an MVA that is independent of the training, validation and test samples, is of utmost importance. We discuss this issue and compare and contrast performance of hold-out and k-fold cross-validation. We have extended the SVM functionality and introduced tools to facilitate cross validation in TMVA and present results based on these improvements.

physics.data-an↗

arXiv2015

Experimental prospects for C, P, T, CP, and CPT tests

Discrete symmetry violation in the weak interaction is central to the Standard Model of particle physics, however the origin of these violations is not well understood. Nor are we able to provide a satisfactory explanation of the Universal dominance of matter over antimatter, an issue related to CP violation. As a result study of discrete symmetry violation remains a topic of broad interest. These proceedings discuss experimental prospects of studying C, P, T, CP and CPT symmetries in a number of contexts, including the use of triple product asymmetries and entangled neutral meson systems.

hep-ex↗

arXiv2014

Standard Model updates and new physics analysis with the Unitarity Triangle fit

We present here the update of the Unitarity Triangle (UT) analysis performed by the UTfit Collaboration within the Standard Model (SM) and beyond. Continuously updated flavour results contribute to improving the precision of several constraints and through the global fit of the CKM parameters and the SM predictions. We also extend the UT analysis to investigate new physics (NP) effects on $ΔF=2$ processes. Finally, based on the NP constraints, we derive upper bounds on the coefficients of the most general $ΔF=2$ effective Hamiltonian. These upper bounds can be translated into lower bounds on the scale of NP that contributes to these low-energy effective interactions.

hep-ph↗

arXiv2014

Neutral meson tests of time-reversal symmetry invariance

The laws of quantum physics can be studied under the mathematical operation T that inverts the direction of time. Strong and electromagnetic forces are known to be invariant under temporal inversion, however the weak force is not. The BaBar experiment recently exploited the quantum-correlated production of pairs of B0 mesons to show that T is a broken symmetry. Here we show that it is possible to perform a wide range of tests of quark flavour changing processes under T in order to validate the Standard Model of particle physics covering b to u, d, s, and c transitions as well as c to u, d and s transitions using entangled B and D pairs created in Y(4S) and psi(3770) decays. We also note that pseudoscalar decays to two spin one particle final states provide an additional set of CP filter bases to use for T violation tests.

hep-ph↗

arXiv2013

T symmetry invariance tests in neutral meson decays

We outline how the time-reversal symmetry T can be systematically used to test the Kobayashi-Maskawa mechanism embedded in the CKM matrix using pairs of B mesons created at the Upsilon(4S) and pairs of D mesons from psi(3770).

hep-ph↗

arXiv2013

Time-dependent CP asymmetries in D and B decays

The measurement of time-dependent CP asymmetries in charm decays can provide a unique insight into the flavor changing structure of the Standard Model. We examine a number of different CP eigenstate decays of D mesons and describe a method that can be used to measure time-dependent CP asymmetries at existing and future experiments, with a preliminary assessment, based on statistical considerations, of their various capabilities. Any asymmetry observed in time-dependent analysis of neutral D mesons could signify new physics. We discuss the measurements required to perform direct and indirect tests of the charm unitarity triangle and the relationship between this and the B_d unitarity triangle. We also highlight that current experimental bounds on DeltaGamma(B_d) translate into a significant systematic uncertainty on the measurement of beta from b to c c-bar s decays.

hep-ph↗

arXiv2012

The complementarity of SuperB with the LHC

The complementarity between results anticipated from SuperB with those from the LHC experiments is discussed here. SuperB can contribute to searches for new physics using indirect constraints via precision tests of the standard model. In addition to the indirect constraints, there are a number of direct searches that can be performed at low energy. There is a well motivated programme of measurements to make at SuperB, the results of which will add to our understanding of possible scenarios of physics beyond the standard model.

hep-ph↗

arXiv2011

The Physics Programme at SuperB

SuperB is a next generation high luminosity $e^+e^-$ collider that will be built at the Cabibbo Laboratory, Tor Vergata, in Italy. The physics goals of this experiment are to search for signs of physics beyond the Standard Model through precision studies of rare or forbidden processes. While the name suggests that $B$ physics is the main goal, this experiment is a Super Flavour Factory, and precision measurements of $B_{u,d,s}$, $D$, $τ$, $Υ$, and $ψ(3770)$ decays as well as spectroscopy and exotica searches form part of a broad physics programme. In addition to searching for new physics (NP) in the form of heavy particles, or violations of laws of physics, data from SuperB will be able to perform precision tests of the Standard Model. I will briefly review of some highlights of the SuperB physics programme.

hep-ex↗

arXiv2011

Time-dependent CP asymmetries in charm decays

The CKM paradigm has been tested thoroughly over the last 40 years in both the neutral $K$ and $B$ systems. The recent discovery of neutral charm meson mixing has prompted the search for CP violation in $D$ decays. We discuss the prospects of performing time-dependent CP asymmetry measurements at facilities either taking data or under construction. Such measurements can (i) provide precision determinations of the charm mixing phase, and (ii) be used to probe for possible new physics effects (and perhaps ultimately constrain the CKM paradigm). We propose the use of the time-dependent asymmetry measurement of $D^0 \to K^+K^-$ decays to measure the phase of charm mixing, where existing experiments that are either under construction or taking data should be able to reach a precision of $<1.5^\circ$, and to use the phase difference between $D^0 \to K^+K^-$ and $D^0 \to π^+π^-$ decays to constrain the angle $β_c$ of the $cu$ unitarity triangle up to theoretical uncertainties from long distance and loop contributions. A large phase difference measured between these modes would indicate new physics.

hep-ex↗