Two topics have recently risen to prominence within the ongoing searches of beyond-Standard Model effects in
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decays: observables that test lepton flavor universality (LFU) and those that test ...lepton flavor violation (LFV). A coherent set of measurements suggests nonstandard LFU effects. General arguments relate LFU to LFV, and the observed size of the former gives hope of observable signals for the latter. We attempt a comprehensive discussion of both theoretical and experimental aspects of these tests. The main final message is that all the instruments necessary to fully establish the putative new effects are at hand, thanks to running experiments and their upgrades. Therefore, this subject stands a concrete chance of ushering in genuinely unexpected discoveries.
We argue that the ordinary commutative and associative algebra of spacetime coordinates (familiar from general relativity) should perhaps be replaced, not by a noncommutative algebra (as in ...noncommutative geometry), but rather by a Jordan algebra (leading to a framework which we term 'Jordan geometry'). We present the Jordan algebra (and representation) that most nearly describes the standard model of particle physics, and we explain that it actually describes a certain (phenomenologically viable) extension of the standard model: by three right-handed (sterile) neutrinos, a complex scalar field φ, and a U(1)B−L gauge boson which is Higgsed by φ. We then note a natural extension of this construction, which describes the SU(4) × SU(2)L × SU(2)R Pati-Salam model. Finally, we discuss a simple and natural Jordan generalization of the exterior algebra of differential forms.
The study of muon properties and decays played a crucial role in the early years of particle physics and contributed over decades to build and consolidate the Standard Model. At present, searches for ...muon decays beyond the Standard Model are performed by exploiting intense beams of muons, and plans exist to upgrade the present facilities or build new ones, which would open new prospects for the quest of new physics in this sector. In this paper I review the present status of the search for muon decays beyond the Standard Model, with a special attention to the most conventional muon lepton flavor violation experiments, but also considering more exotic scenarios and future outlooks.
Rare charm decays offer the unique possibility to explore flavor-changing neutral-currents in the up-sector within the Standard Model and beyond. Due to the lack of effective methods to reliably ...describe its low energy dynamics, rare charm decays have been considered as less promising for long. However, this lack does not exclude the possibility to perform promising searches for New Physics per se, but a different philosophy of work is required. Exact or approximate symmetries of the Standard Model allow to construct clean null-test observables, yielding an excellent road to the discovery of New Physics, complementing the existing studies in the down-sector. In this review, we summarize the theoretical and experimental status of rare charm
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transitions, as well as opportunities for current and future experiments such as LHCb, Belle II, BES III, the FCC-ee and proposed tau-charm factories. We also use the most recent experimental results to report updated limits on lepton-flavor conserving and lepton-flavor violating Wilson coefficients.
Although the two-loop renormalization group equations for a general gauge field theory have been known for quite some time, deriving them for specific models has often been difficult in practice. ...This is mainly due to the fact that, albeit straightforward, the involved calculations are quite long, tedious and prone to error. The present work is an attempt to facilitate the practical use of the renormalization group equations in model building. To that end, we have developed two completely independent sets of programs written in Python and Mathematica, respectively. The Mathematica scripts will be part of an upcoming release of SARAH 4. The present article describes the collection of Python routines that we dubbed PyR@TE which is an acronym for "Python Renormalization group equations At Two-loop for Everyone". In PyR@TE, once the user specifies the gauge group and the particle content of the model, the routines automatically generate the full two-loop renormalization group equations for all (dimensionless and dimensionful) parameters. The results can optionally be exported to Latex and Mathematica, or stored in a Python data structure for further processing by other programs. For ease of use, we have implemented an interactive mode for PyR@TE in form of an IPython Notebook. As a first application, we have generated with PyR@TE the renormalization group equations for several non-supersymmetric extensions of the Standard Model and found some discrepancies with the existing literature.
This article reviews the Little Higgs models of electroweak symmetry breaking and their phenomenology. Little Higgs models incorporate a light composite Higgs boson and remain perturbative until a ...scale of order 10 TeV, as preferred by precision electroweak data. The collective symmetry breaking mechanism, which forms the basis of Little Higgs models, is introduced. An explicit, fully realistic implementation of this mechanism, the Littlest Higgs model, is then discussed in some detail. Several other implementations, including simple group models and models with T parity, are also reviewed. Precision electroweak constraints on a variety of Little Higgs models are summarized. If a Little Higgs model is realized in nature, the predicted new particles should be observable at the Large Hadron Collider (LHC). The expected signatures, as well as the experimental sensitivities and the possible strategies for confirming the Little Higgs origin of new particles, are discussed. Finally, several other related topics are briefly reviewed, including the ultraviolet completions of Little Higgs models, as well as the implications of these models for flavor physics and cosmology.
SModelS Database Update v1.2.3 K. Khosa, Charanjit; Kraml, Sabine; Lessa, Andre ...
Letters in high energy physics,
03/2020, Volume:
2020, Issue:
1
Journal Article
Peer reviewed
Open access
We present an update of the SModelS database with simplified model results from 13 ATLAS and 10 CMS searches for supersymmetry at Run 2. This includes 5 ATLAS and 1 CMS analyses for full Run 2 ...luminosity, i.e., close to 140/fb of data. In total, 76 official upper limit and efficiency map results have been added. Moreover, 21 efficiency map results have been produced by us using MadAnalysis5, to improve the coverage of gluino-squark production. The constraining power of the new database, v1.2.3, is compared to that of the previous release, v1.2.2. SModelS v1.2.3 is publicly available and can readily be employed for physics studies.
Tree boosting for learning EFT parameters Chatterjee, Suman; Frohner, Nikolaus; Lechner, Lukas ...
Computer physics communications,
August 2022, 2022-08-00, Volume:
277
Journal Article
Peer reviewed
Open access
We present a new tree boosting algorithm designed for the measurement of parameters in the context of effective field theory (EFT). To construct the algorithm, we interpret the optimized loss ...function of a traditional decision tree as the maximal Fisher information in Poisson counting experiments. We promote the interpretation to general EFT predictions and develop a suitable boosting method. The resulting “Boosted Information Tree” algorithm approximates the score, the derivative of the log-likelihood function with respect to the parameter. It thus provides a sufficient statistic in the vicinity of a reference point in parameter space where the estimator is trained. The training exploits per-event information of likelihood ratios for different theory parameter values available in the simulated EFT data sets.
Program Title: BIT (Boosted Information Trees)
CPC Library link to program files:https://doi.org/10.17632/9fjyb5hyxt.1
Developer's repository link:https://github.com/HephyAnalysisSW/BIT
Licensing provisions: GPLv3
Programming language: Python2 and Python3
Nature of problem: Providing a discriminator for parameter estimation in the context of the standard model effective field theory.
Solution method: A tree-based algorithm exploits “augmented” information of the simulated training data set to regress in the score function and thereby provides a sufficient test statistic of an EFT parameter.
The James Webb Space Telescope (JWST) is unveiling astounding results about the first few hundred million years of life of the Universe, delivering images of galaxies at very high redshifts. Here, we ...develop a UV luminosity function model for high-redshift galaxies, considering parameters such as the stellar formation rate, dust extinction, and halo mass function. Calibration of this luminosity function model using UV luminosity data at redshifts z=4-7 yields optimal parameter values. Testing the model against data at higher redshifts reveals successful accommodation of the data at z=8-9, but challenges emerge at z≃13. Our findings suggest a negligible role of dust extinction at the highest redshifts, prompting a modification of the stellar formation rate to incorporate a larger fraction of luminous objects per massive halo, consistently with similar recent studies. This effect could be attributed to mundane explanations such as unknown evolution of standard astrophysics at high redshift or to the existence of exotic objects at high redshift. We comment on this latter possibility.
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