arXiv subjects

Tancredi Carli

Publications and source records attributed to Tancredi Carli.

16 recordsLinked to original sources

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

A continuous integration and web framework in support of the ATLAS Publication Process

The ATLAS collaboration defines methods, establishes procedures, and organises advisory groups to manage the publication processes of scientific papers, conference papers, and public notes. All stages are managed through web systems, computing programs, and tools that are designed and developed by the collaboration. A framework called FENCE is integrated into the CERN GitLab software repository, to automatically configure workspaces where each analysis can be documented by the analysis team and managed by the relevant coordinators. Continuous integration is used to guide the writers in applying consistent and correct formatting when preparing papers to be submitted to scientific journals. Additional software assures the correctness of other aspects of each paper, such as the lists of collaboration authors, funding agencies, and foundations. The framework and the workflow therein provide automatic and easy support to the researchers and facilitates each phase of the publication process, allowing authors to focus on the article contents. The framework and its integration with the most up to date and efficient tools has consequently provided a more professional and efficient automatized work environment to the whole collaboration.

cs.DL↗

arXiv2016

Containment and resolution of hadronic showers at the FCC

The particles produced at a potential Future Circular Collider with $\sqrt{s}$ = 100 TeV are of unprecented energies. In this document we present the hadronic shower containment and resolution parametrizations based on Geant4 simulations for the Hadronic calorimetry needed for conceptual detector design at this energy. The Geant4 toolkit along with FTFP\_BERT physics list are used in this study. Comparisons are made with test-beam data from the ATLAS Tile hadronic calorimeter. These simulations motivate a 12 $λ$ calorimeter in order to contain at 98% level TeV single hadron showers and multi-TeV jets and keep a pion energy resolution constant term of 3%.

physics.ins-det↗

arXiv2015

Studies of Quantum Chromodynamics at the LHC

A successful description of hadron-hadron collision data demands a profound understanding of quantum chromodynamics. Inevitably, the complexity of strong-interaction phenomena requires the use of a large variety of theoretical techniques -- from perturbative cross-section calculations up to the modelling of exclusive hadronic final states. Together with the unprecedented precision of the data provided by the experiments in the first running period of the LHC, a solid foundation of hadron-hadron collision physics at the TeV scale could be established that allowed the discovery of the Higgs boson and that is vital for estimating the background in searches for new phenomena. This chapter on studies of quantum chromodynamics at the LHC is part of a recent book on the results of LHC Run 1 and presents the advances in theoretical methods side-by-side with related key measurements in an integrated approach.

hep-ex↗

arXiv2010

Hadronic final states in DIS with Sherpa

We present an extension of the multi-purpose Monte-Carlo event generator Sherpa for processes in deeply inelastic lepton-nucleon scattering. Hadronic final states in this kinematical setting are characterised by the presence of multiple kinematical scales, which were up to now accounted for only by specific resummations in individual kinematical regions. An extension of a known method for merging truncated parton showers with higher-order tree-level matrix elements allows to obtain predictions which are reliable in all kinematical limits.

hep-ph↗

arXiv2009

Hadronic final states in deep-inelastic scattering with Sherpa

We extend the multi-purpose Monte-Carlo event generator Sherpa to include processes in deeply inelastic lepton-nucleon scattering. Hadronic final states in this kinematical setting are characterised by the presence of multiple kinematical scales, which were up to now accounted for only by specific resummations in individual kinematical regions. Using an extension of the recently introduced method for merging truncated parton showers with higher-order tree-level matrix elements, it is possible to obtain predictions which are reliable in all kinematical limits. Different hadronic final states, defined by jets or individual hadrons, in deep-inelastic scattering are analysed and the corresponding results are compared to HERA data. The various sources of theoretical uncertainties of the approach are discussed and quantified. The extension to deeply inelastic processes provides the opportunity to validate the merging of matrix elements and parton showers in multi-scale kinematics inaccessible in other collider environments. It also allows to use HERA data on hadronic final states in the tuning of hadronisation models.

hep-ph↗

arXiv2009

A posteriori inclusion of parton density functions in NLO QCD final-state calculations at hadron colliders: The APPLGRID Project

A method to facilitate the consistent inclusion of cross-section measurements based on complex final-states from HERA, TEVATRON and the LHC in proton parton density function (PDF) fits has been developed. This can be used to increase the sensitivity of LHC data to deviations from Standard Model predictions. The method stores perturbative coefficients of NLO QCD calculations of final-state observables measured in hadron colliders in look-up tables. This allows the posteriori inclusion of parton density functions (PDFs), and of the strong coupling, as well as the a posteriori variation of the renormalisation and factorisation scales in cross-section calculations. The main novelties in comparison to original work on the subject are the use of higher-order interpolation, which substantially improves the trade-off between accuracy and memory use, and a CPU and computer memory optimised way to construct and store the look-up table using modern software tools. It is demonstrated that a sufficient accuracy on the cross-section calculation can be achieved with reasonably small look-up table size by using the examples of jet production and electro-weak boson (Z, W) production in proton-proton collisions at a center-of-mass energy of 14 TeV at the LHC. The use of this technique in PDF fitting is demonstrated in a PDF-fit to HERA data and simulated LHC jet cross-sections as well as in a study of the jet cross-section uncertainties at various centre-of-mass energies.

hep-ph↗

arXiv2009

PDE-Foam - a probability-density estimation method using self-adapting phase-space binning

Probability Density Estimation (PDE) is a multivariate discrimination technique based on sampling signal and background densities defined by event samples from data or Monte-Carlo (MC) simulations in a multi-dimensional phase space. In this paper, we present a modification of the PDE method that uses a self-adapting binning method to divide the multi-dimensional phase space in a finite number of hyper-rectangles (cells). The binning algorithm adjusts the size and position of a predefined number of cells inside the multi-dimensional phase space, minimising the variance of the signal and background densities inside the cells. The implementation of the binning algorithm PDE-Foam is based on the MC event-generation package Foam. We present performance results for representative examples (toy models) and discuss the dependence of the obtained results on the choice of parameters. The new PDE-Foam shows improved classification capability for small training samples and reduced classification time compared to the original PDE method based on range searching.

physics.data-an↗

arXiv2005

A posteriori inclusion of PDFs in NLO QCD final-state calculations

Any NLO calculation of a QCD final-state observable involves Monte Carlo integration over a large number of events. For DIS and hadron colliders this must usually be repeated for each new PDF set, making it impractical to consider many `error' PDF sets, or carry out PDF fits. Here we discuss ``a posteriori'' inclusion of PDFs, whereby the Monte Carlo run calculates a grid (in x and Q) of cross section weights that can subsequently be combined with an arbitrary PDF. The procedure is numerically equivalent to using an interpolated form of the PDF. The main novelty relative to prior work is the use of higher-order interpolation, which substantially improves the tradeoff between accuracy and memory use. An accuracy of about 0.01% has been reached for the single inclusive cross-section in the central rapidity region |y|<0.5 for jet transverse momenta from 100 to 5000 GeV. This method should facilitate the consistent inclusion of final-state data from HERA, Tevatron and LHC in PDF fits, thus helping to increase the sensitivity of LHC to deviations from standard Model predictions.

hep-ph↗

arXiv2004

Events with Isolated Charged Leptons and Large Missing Transverse Momentum at HERA

Striking events with isolated charged leptons, large missing transverse momentum and large transverse momentum of the hadronic final state were observed at the electron proton collider HERA in a data sample corresponding to a luminosity of about 130 pb-1. The H1 collaboration observed 11 events with isolated electrons or muons and with transverse momentum above 25 GeV. Only 3.4+-0.6 events were expected from Standard Model (SM) processes. Six of these events have a transverse momentum of greater than 40 GeV, while 1.3+-0.3 events were expected. The ZEUS collaboration observed good agreement with the SM. However, ZEUS found two events with a similar event topology, but tau leptons instead of electrons or muons in the final state. Only 0.2+-0.05 events were expected from SM processes. For various hypotheses the compatibility of the experimental results was investigated with respect to the SM and with respect to possible explanations beyond the SM. Prospects for the high-luminosity HERA-II data taking period are given.

hep-ph↗

arXiv2003

Observation of Events with Isolated Charged Leptons and Large Missing Tra nsverse Momentum and of Events with Multi-Electrons at HERA

Striking events with isolated charged leptons, large missing transverse momentum and large transverse momentum of the hadronic final state (PTX) have been observed at the electron proton collider HERA. In the full HERA-I data sample corresponding to an integrated luminosity of about 130 invpb, the H1 experiment observes 10 events with isolated electrons or muons and with PTX >25 GeV. Only 2.9 pm 0.4 events are expected from Standard Model (SM) processes. Six of these events have PTX >40 GeV, while 1.1 pm 0.2 events are expected. The ZEUS experiment observes good agreement with the SM. However, in a preliminary search ZEUS has found two events with a similar event topology, but tau-leptons instead of electrons or muons in the final state . Only 0.12 pm 0.02 events are expected from SM processes. Moreover, six events with two or more electrons forming an invariant mass bigger than 100 GeV have been observed by the H1 experiment. Three events have two electrons and three events have three electrons, while only 0.25 events are expected in each case. The ZEUS measurement is in agreement with the SM expectation.

hep-ph↗

arXiv2001

Small-x QCD Effects in Particle Collisions at High Energies

Recent theoretical developments to calculate cross sections of hadronic objects in the high energy limit are summarised and experimental attempts to establish the need for new QCD effects connected with a resummation of small hadron momentum fractions x are reviewed. The relation between small-$x$ parton dynamics and the phenomenon of diffraction is briefly out-lined. In addition, a search for a novel, non-perturbative QCD effect, the production of QCD instanton induced events, is presented.

hep-ph↗

arXiv1999

Renormalisation Scale Dependencies in Dijet Production at HERA

Different choices of the renormalisation scale (muren) can be used to describe hard scattering processes with two jets at large transverse momentum in deep-inelastic scattering at HERA by fixed order perturbative QCD calculations. For leading (LO) and next-to-leading order (NLO) calculations the simplest choices, Q2, the virtuality of the incoming photon, and the mean squared transverse momenta of the two jets ET2, are studied in different kinematic regimes. It is found that only if both Q2 and ET2 are large, the NLO calculation is stable with respect to numerical variations of muren while the LO calculation strongly depends on it. If only one of the two scales, either Q2 or ET2, is large, the NLO is more stable than the LO calculation, but exhibits nevertheless a strong residual scale dependence. When both scales are relatively small, large scale dependencies are found in both cases. Moreover, large differences between the LO and NLO calculation are found. Generally, the use of ET2 as renormalisation scale is favoured over Q2, since scale dependencies are less pronounced and NLO corrections are smaller.

hep-ph↗

arXiv1999

Latest Highlights from the H1 Collaboration

Recent data obtained in ep collisions at HERA by the H1 collaboration are presented: searches for new phenomena beyond the Standard Model, measurement of the inclusive neutral and charged current cross sections and of the proton structure function, determination of the gluon density in the proton and photon from jet productions, measurement and interpretation of event shapes in the current region of the Breit frame, test of the parton evolution at low x and of the diffractive production mechanism.

hep-ph↗

arXiv1997

Jet Production in Deep-inelastic Scattering at HERA

The main experimental results on jet production at HERA are reviewed. A study of jet shapes shows that the internal structure of jets is well understood. The potential to accurately determine the strong coupling constant using jet rates is discussed. First attempts to extract the gluon density in next-to-leading order are presented. Although fixed order perturbative QCD is able to describe the shape of most variables associated to the hard subprocess leading to jets, it does not reproduce the absolute dijet rate over a large phase space region.

hep-ph↗

arXiv1997

Hadronic Final State in Deep-inelastic Scattering at HERA

Data on the hadronic final state of deep-inelastic events at the ep collider HERA are reviewed. Fragmentation properties in the current region extracted from charged particle spectra are compared to e+e- and fixed target experiments at lower center of mass energies. A measurement of the strong coupling constant from integrated jet rates is presented and prospects to extract the gluon density in the proton by tagging vector mesons are discussed. Data on the inclusive mean transverse energy together with the transverse momentum distribution of single charged particles indicate an increased gluon activity in the central rapidity region when the phase space is enlarged. The measurement of the forward jet cross-section is discussed. Keeping the phase space fixed, the mean transverse energy and the mean charged multiplicity for certain rapidity ranges is found to behave analogously to ppbar collisions.

hep-ph↗