| 1. |
- Abercrombie, Daniel, et al.
(författare)
-
Dark Matter benchmark models for early LHC Run-2 Searches : Report of the ATLAS/CMS Dark Matter Forum
- 2020
-
Ingår i: Physics of the Dark Universe. - : Elsevier BV. - 2212-6864. ; 27
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 2. |
- Allanach, Benjamin C., et al.
(författare)
-
Simple and statistically sound strategies for analysing physical theories
- 2022
-
Ingår i: Reports on progress in physics (Print). - : Institute of Physics Publishing (IOPP). - 0034-4885 .- 1361-6633. ; 85:5
-
Forskningsöversikt (refereegranskat)abstract
- Physical theories that depend on many parameters or are tested against data from many different experiments pose unique challenges to statistical inference. Many models in particle physics, astrophysics and cosmology fall into one or both of these categories. These issues are often sidestepped with statistically unsound ad hoc methods, involving intersection of parameter intervals estimated by multiple experiments, and random or grid sampling of model parameters. Whilst these methods are easy to apply, they exhibit pathologies even in low-dimensional parameter spaces, and quickly become problematic to use and interpret in higher dimensions. In this article we give clear guidance for going beyond these procedures, suggesting where possible simple methods for performing statistically sound inference, and recommendations of readily-available software tools and standards that can assist in doing so. Our aim is to provide any physicists lacking comprehensive statistical training with recommendations for reaching correct scientific conclusions, with only a modest increase in analysis burden. Our examples can be reproduced with the code publicly available at Zenodo.
|
|
| 3. |
- Athron, Peter, et al.
(författare)
-
A global fit of the MSSM with GAMBIT
- 2017
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 77:12
-
Tidskriftsartikel (refereegranskat)abstract
- We study the seven-dimensional Minimal Super-symmetric Standard Model (MSSM7) with the new GAMBIT software framework, with all parameters defined at the weak scale. Our analysis significantly extends previous weak-scale, phenomenological MSSM fits, by adding more and newer experimental analyses, improving the accuracy and detail of theoretical predictions, including dominant uncertainties from the Standard Model, the Galactic dark matter halo and the quark content of the nucleon, and employing novel and highly-efficient statistical sampling methods to scan the parameter space. We find regions of the MSSM7 that exhibit co-annihilation of neutralinos with charginos, stops and sbottoms, as well as models that undergo resonant annihilation via both light and heavy Higgs funnels. We find high-likelihood models with light charginos, stops and sbottoms that have the potential to be within the future reach of the LHC. Large parts of our preferred parameter regions will also be accessible to the next generation of direct and indirect dark matter searches, making prospects for discovery in the near future rather good.
|
|
| 4. |
- Athron, Peter, et al.
(författare)
-
GAMBIT : the global and modular beyond-the-standard-model inference tool
- 2017
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 77:11
-
Tidskriftsartikel (refereegranskat)abstract
- We describe the open-source global fitting package GAMBIT: the Global And Modular Beyond-the-Standard-Model Inference Tool. GAMBIT combines extensive calculations of observables and likelihoods in particle and astroparticle physics with a hierarchical model database, advanced tools for automatically building analyses of essentially any model, a flexible and powerful system for interfacing to external codes, a suite of different statistical methods and parameter scanning algorithms, and a host of other utilities designed to make scans faster, safer and more easily-extendible than in the past. Here we give a detailed description of the framework, its design and motivation, and the current models and other specific components presently implemented in GAMBIT. Accompanying papers deal with individual modules and present flrst GAMBIT results. GAMBIT can be downloaded from gambit.hepforge.org.
|
|
| 5. |
- Athron, Peter, et al.
(författare)
-
GAMBIT : the global and modular beyond-the-standard-model inference tool
- 2018
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 78:2
-
Tidskriftsartikel (refereegranskat)abstract
- In Ref. (GAMBIT Collaboration: Athron et. al., Eur. Phys. J. C. arXiv: 1705.07908, 2017) we introduced the global-fitting framework GAMBIT. In this addendum, we describe a new minor version increment of this package. GAMBIT 1.1 includes full support for Mathematica backends, which we describe in some detail here. As an example, we backend SUSYHD (Vega and Villadoro, JHEP 07: 159, 2015), which calculates the mass of the Higgs boson in the MSSM from effective field theory. We also describe updated likelihoods in PrecisionBit and DarkBit, and updated decay data included in DecayBit.
|
|
| 6. |
- Athron, Peter, et al.
(författare)
-
Global fits of GUT-scale SUSY models with GAMBIT
- 2017
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 77:12
-
Tidskriftsartikel (refereegranskat)abstract
- We present the most comprehensive global fits to date of three supersymmetric models motivated by grand unification: the Constrained Minimal Supersymmetric Standard Model (CMSSM), and its Non-Universal Higgs Mass generalisations NUHM1 and NUHM2. We include likelihoods from a number of direct and indirect dark matter searches, a large collection of electroweak precision and flavour observables, direct searches for supersymmetry at LEP and Runs I and II of the LHC, and constraints from Higgs observables. Our analysis improves on existing results not only in terms of the number of included observables, but also in the level of detail with which we treat them, our sampling techniques for scanning the parameter space, and our treatment of nuisance parameters. We show that stau co-annihilation is now ruled out in the CMSSM at more than 95% confidence. Stop co-annihilation turns out to be one of the most promising mechanisms for achieving an appropriate relic density of darkmatter in all threemodels, whilst avoiding all other constraints. We find high-likelihood regions of parameter space featuring light stops and charginos, making them potentially detectable in the near future at the LHC. We also show that tonne-scale direct detection will play a largely complementary role, probing large parts of the remaining viable parameter space, including essentially all models with multi-TeV neutralinos.
|
|
| 7. |
- Athron, Peter, et al.
(författare)
-
Status of the scalar singlet dark matter model
- 2017
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 77:8
-
Tidskriftsartikel (refereegranskat)abstract
- One of the simplest viable models for dark matter is an additional neutral scalar, stabilised by a symmetry. Using the GAMBIT package and combining results from four independent samplers, we present Bayesian and frequentist global fits of this model. We vary the singlet mass and coupling along with 13 nuisance parameters, including nuclear uncertainties relevant for direct detection, the local dark matter density, and selected quark masses and couplings. We include the dark matter relic density measured by Planck, direct searches with LUX, PandaX, SuperCDMS and XENON100, limits on invisible Higgs decays from the Large Hadron Collider, searches for high-energy neutrinos from dark matter annihilation in the Sun with IceCube, and searches for gamma rays from annihilation in dwarf galaxies with the Fermi-LAT. Viable solutions remain at couplings of order unity, for singlet masses between the Higgs mass and about 300 GeV, and at masses above 1 TeV. Only in the latter case can the scalar singlet constitute all of dark matter. Frequentist analysis shows that the low-mass resonance region, where the singlet is about half the mass of the Higgs, can also account for all of dark matter, and remains viable. However, Bayesian considerations show this region to be rather fine-tuned.
|
|
| 8. |
- Balázs, Csaba, et al.
(författare)
-
ColliderBit : a GAMBIT module for the calculation of high-energy collider observables and likelihoods
- 2017
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 77:11
-
Tidskriftsartikel (refereegranskat)abstract
- We describe ColliderBit, a new code for the calculation of high energy collider observables in theories of physics beyond the Standard Model (BSM). ColliderBit features a generic interface to BSM models, a unique parallelised Monte Carlo event generation scheme suitable for large-scale supercomputer applications, and a number of LHC analyses, covering a reasonable range of the BSM signatures currently sought by ATLAS and CMS. ColliderBit also calculates likelihoods for Higgs sector observables, and LEP searches for BSM particles. These features are provided by a combination of new code unique to ColliderBit, and interfaces to existing state-of-the-art public codes. ColliderBit is both an important part of the GAMBIT framework for BSM inference, and a standalone tool for efficiently applying collider constraints to theories of new physics.
|
|
| 9. |
- Bellm, Johannes, et al.
(författare)
-
Jet cross sections at the LHC and the quest for higher precision
- 2020
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 80:2
-
Tidskriftsartikel (refereegranskat)abstract
- We perform a phenomenological study of Z plus jet, Higgs plus jet and di-jet production at the Large Hadron Collider. We investigate in particular the dependence of the leading jet cross section on the jet radius as a function of the jet transverse momentum. Theoretical predictions are obtained using perturbative QCD calculations at the next-to and next-to-next-to-leading order, using a range of renormalization and factorization scales. The fixed order predictions are compared to results obtained from matching next-to-leading order calculations to parton showers. A study of the scale dependence as a function of the jet radius is used to provide a better estimate of the scale uncertainty for small jet sizes. The non-perturbative corrections as a function of jet radius are estimated from different generators.
|
|
| 10. |
- Bierlich, Christian, et al.
(författare)
-
Confronting experimental data with heavy-ion models : Rivet for heavy ions
- 2020
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 80:5
-
Tidskriftsartikel (refereegranskat)abstract
- The Rivet library is an important toolkit in particle physics, and serves as a repository for analysis data and code. It allows for comparisons between data and theoretical calculations of the final state of collision events. This paper outlines several recent additions and improvements to the framework to include support for analysis of heavy ion collision simulated data. The paper also presents examples of these recent developments and their applicability in implementing concrete physics analyses.
|
|
| 11. |
- Bierlich, Christian, et al.
(författare)
-
Robust independent validation of experiment and theory : RIVET version 3
- 2020
-
Ingår i: SciPost Physics. - 2542-4653. ; 8:2
-
Tidskriftsartikel (refereegranskat)abstract
- First released in 2010, the RIVET library forms an important repository for analysis code, facilitating comparisons between measurements of the final state in particle collisions and theoretical calculations of those final states. We give an overview of RIVET’s current design and implementation, its uptake for analysis preservation and physics results, and summarise recent developments including propagation of MC systematic-uncertainty weights, heavy-ion and ep physics, and systems for detector emulation. In addition, we provide a short user guide that supplements and updates the RIVET user manual.
|
|
| 12. |
- Bothmann, Enrico, et al.
(författare)
-
A standard convention for particle-level Monte Carlo event-variation weights
- 2023
-
Ingår i: SciPost Physics Core. - 2666-9366. ; 6:1
-
Tidskriftsartikel (refereegranskat)abstract
- Streams of event weights in particle-level Monte Carlo event generators are a convenient and immensely CPU-efficient approach to express systematic uncertainties in phenomenology calculations, providing systematic variations on the nominal prediction within a single event sample. But the lack of a common standard for labelling these variation streams across different tools has proven to be a major limitation for event-processing tools and analysers alike. Here we propose a well-defined, extensible community standard for the naming, ordering, and interpretation of weight streams that will serve as the basis for semantically correct parsing and combination of such variations in both theoretical and experimental studies.
|
|
| 13. |
- Buckley, Andy, et al.
(författare)
-
General-purpose event generators for LHC physics
- 2011
-
Ingår i: Physics Reports. - : Elsevier BV. - 0370-1573. ; 504:5, s. 145-233
-
Forskningsöversikt (refereegranskat)abstract
- We review the physics basis, main features and use of general-purpose Monte Carlo event generators for the simulation of proton-proton collisions at the Large Hadron Collider. Topics included are: the generation of hard scattering matrix elements for processes of interest, at both leading and next-to-leading QCD perturbative order; their matching to approximate treatments of higher orders based on the showering approximation; the parton and dipole shower formulations; parton distribution functions for event generators; non-perturbative aspects such as soft QCD collisions, the underlying event and diffractive processes; the string and cluster models for hadron formation; the treatment of hadron and tau decays; the inclusion of QED radiation and beyond Standard Model processes. We describe the principal features of the ARIADNE, Herwig++, PYTHIA 8 and SHERPA generators, together with the Rivet and Professor validation and tuning tools, and discuss the physics philosophy behind the proper use of these generators and tools. This review is aimed at phenomenologists wishing to understand better how parton-level predictions are translated into hadron-level events as well as experimentalists seeking a deeper insight into the tools available for signal and background simulation at the LHC. (C) 2011 Elsevier B.V. All rights reserved.
|
|
| 14. |
|
|
| 15. |
- Buckley, Andy, et al.
(författare)
-
Rivet user manual
- 2013
-
Ingår i: Computer Physics Communications. - : Elsevier BV. - 0010-4655. ; 184:12, s. 2803-2819
-
Tidskriftsartikel (refereegranskat)abstract
- This is the manual and user guide for the Rivet system for the validation and tuning of Monte Carlo event generators. As well as the core Rivet library, this manual describes the usage of the rivet program and the AGILe generator interface library. The depth and level of description is chosen for users of the system, starting with the basics of using validation code written by others, and then covering sufficient details to write new Rivet analyses and calculational components. Program summary Program title: Rivet Catalogue identifier: AEPS_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEPS_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 571126 No. of bytes in distributed program, including test data, etc.: 4717522 Distribution format: tar.gz Programming language: C++, Python. Computer: PC running Linux, Mac. Operating system: Linux, Mac OS. RAM: 20 MB Classification: 11.9, 11.2. External routines: HepMC (https://savannah.cern.ch/projects/hepmc/), GSL (http://www.gnu.org/software/gsl/manual/gsl-ref.html), FastJet (http://fastjet.fr/), Python (http://www.python.org/), Swig (http://www.swig.org/), Boost (http://www.boostsoftware.com/), YAML (http://www.yaml.org/spec/1.2/spec.html) Nature of problem: Experimental measurements from high-energy particle colliders should be defined and stored in a general framework such that it is simple to compare theory predictions to them. Rivet is such a framework, and contains at the same time a large collection of existing measurements. Solution method: Rivet is based on HepMC events, a standardised output format provided by many theory simulation tools. Events are processed by Rivet to generate histograms for the requested list of analyses, incorporating all experimental phase space cuts and histogram definitions. Restrictions: Cannot calculate statistical errors for correlated events as they appear in NLO calculations. Unusual features: It is possible for the user to implement and use their own custom analysis as a module without having to modify the main Rivet code/installation. Running time: Depends on the number and complexity of analyses being applied, but typically a few hundred events per second. (C) 2013 Elsevier B.V. All rights reserved.
|
|
| 16. |
- Buckley, Andy, et al.
(författare)
-
Systematic event generator tuning for the LHC
- 2010
-
Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 65:1-2, s. 331-357
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedIn this article we describe Professor, a new program for tuning model parameters of Monte Carlo event generators to experimental data by parameterising the per-bin generator response to parameter variations and numerically optimising the parameterised behaviour. Simulated experimental analysis data is obtained using the Rivet analysis toolkit. This paper presents the Professor procedure and implementation, illustrated with the application of the method to tunes of the Pythia 6 event generator to data from the LEP/SLD and Tevatron experiments. These tunes are substantial improvements on existing standard choices, and are recommended as base tunes for LHC experiments, to be themselves systematically improved upon when early LHC data is available.
|
|
| 17. |
- Buckley, Andy, et al.
(författare)
-
The HepMC3 event record library for Monte Carlo event generators
- 2021
-
Ingår i: Computer Physics Communications. - : Elsevier BV. - 0010-4655. ; 260
-
Tidskriftsartikel (refereegranskat)abstract
- In high-energy physics, Monte Carlo event generators (MCEGs) are used to simulate the interactions of high energy particles. MCEG event records store the information on the simulated particles and their relationships, and thus reflect the simulated evolution of physics phenomena in each collision event. We present the HepMC3 library, a next-generation framework for MCEG event record encoding and manipulation, which builds on the functionality of its widely-used predecessors to enable more sophisticated algorithms for event-record analysis. As compared to previous versions, the event record structure has been simplified, while adding the possibility to encode arbitrary information. The I/O functionality has been extended to support common input and output formats of various HEP MCEGs, including formats used in Fortran MCEGs, the formats established by the HepMC2 library, and binary formats such as ROOT; custom input or output handlers may also be used. HepMC3 is already supported by popular modern MCEGs and can replace the older HepMC versions in many others.
|
|
| 18. |
- Valassi, Andrea, et al.
(författare)
-
Challenges in Monte Carlo Event Generator Software for High-Luminosity LHC
- 2021
-
Ingår i: Computing and Software for Big Science. - : Springer Science and Business Media LLC. - 2510-2044 .- 2510-2036. ; 5:1
-
Tidskriftsartikel (refereegranskat)abstract
- We review the main software and computing challenges for the Monte Carlo physics event generators used by the LHC experiments, in view of the High-Luminosity LHC (HL-LHC) physics programme. This paper has been prepared by the HEP Software Foundation (HSF) Physics Event Generator Working Group as an input to the LHCC review of HL-LHC computing, which has started in May 2020.
|
|
