arXiv subjects

Janusz Rosiek

Publications and source records attributed to Janusz Rosiek.

At least 19 recordsLinked to original sources

arXiv2025

Double Higgs Production via Vector Boson Fusion in SMEFT

While gluon fusion dominates Higgs pair production at the LHC, vector boson fusion (VBF) offers a unique window into Beyond the Standard Model (BSM) physics through its distinctive kinematic features and direct sensitivity to Higgs-vector boson interactions. We perform a comprehensive analysis of double Higgs production via VBF in the Standard Model Effective Field Theory (SMEFT), systematically investigating how dimension-6 and dimension-8 bosonic operators - particularly those involving field derivatives - can enhance the production rate. We identify the most relevant Wilson coefficients (WCs) affecting the trilinear Higgs coupling ($hhh$) and Higgs-vector boson interactions ($hVV$, $hhVV$). Using constraints from global fits and interpolating fit results for unconstrained WCs with Naive Dimensional Analysis, we assess their effects on the $VV \to hh$ ($V = W,Z$) scattering amplitudes and cross-sections. Our analysis includes a study of EFT convergence and validity in models with scalar extensions of the SM. Numerical simulations for the planned High-Luminosity LHC experiment (HL-LHC) in general reveal only a modest and challenging to detect enhancement of the VBF di-Higgs production rate over the SM prediction. However, we show that in optimistic scenarios, such a process could be observed at the HL-LHC. In certain cases, when the enhancement is dominated by the dimension-6 or dimension-8 operators containing field derivatives (and thus leading to stronger energy-dependent effects), this channel becomes competitive with di-Higgs production via gluon fusion. This work highlights the role of VBF di-Higgs production as a complementary channel for probing anomalous Higgs couplings and their impact on BSM physics.

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arXiv2024

Theoretical constraints on models with vector-like fermions

We provide a set of theoretical constraints on models in which the Standard Model field content is extended by vector-like fermions and in some cases also by a real scalar singlet. Our approach is based on the study of electroweak vacuum stability, perturbativity of model couplings and gauge couplings unification with the use of renormalization group equations. We show that careful analysis of these issues leads to strong constraints on the parameter space of the considered models. This, in turn, has important implications for phenomenology, as we show using examples of the double Higgs boson production, electroweak precision observables, and the electroweak phase transition.

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arXiv2024

Exploring CP violation in $H \to τ^+ τ^- γ$

We propose a method of measuring the CP-odd part of the Yukawa interaction of Higgs boson and $τ$ leptons by observing the forward-backward asymmetry in the decay $H \to τ^+ \, τ^- \, γ$. The source of such asymmetry is the interference of the CP-even loop-level contribution coming from $H \to Z \, γ\to τ^+ \, τ^- \, γ$ decay channel with the contribution from tree-level CP-odd Yukawa interaction. We find that the CP violating effect is maximum when the invariant mass of the $τ^+ \, τ^-$ pair is equal to the mass of the $Z$ boson. We propose and utilise various Dalitz plot asymmetries to quantify the maximal size of the asymmetry and perform Monte Carlo simulations to study the feasibility of measuring it in the high luminosity phase of the Large Hadron Collider (HL-LHC).

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arXiv2024

Computing Tools for Effective Field Theories

In recent years, theoretical and phenomenological studies with effective field theories have become a trending and prolific line of research in the field of high-energy physics. In order to discuss present and future prospects concerning automated tools in this field, the SMEFT-Tools 2022 workshop was held at the University of Zurich from 14th-16th September 2022. The current document collects and summarizes the content of this workshop.

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arXiv2023

Probing the non-standard neutrino interactions using quantum statistics

Using the well established principles of Lorentz invariance, CP and CPT symmetry, and quantum statistics we do a model-independent study of effects of possible non-standard couplings of (Dirac and Majorana) neutrinos. The study is sensitive to the different quantum statistical properties of the Dirac and Majorana neutrinos which, contrary to neutrino-mediated processes of lepton number violation, could lead to observable effects not suppressed by the small ratios of neutrino and heavier particle masses. For processes with a neutrino-antineutrino pair of the same flavor in the final state, we formulate the ``Dirac Majorana confusion theorem (DMCT)'' showing why it is normally very difficult to observe the different behaviour of both kinds of neutrinos in experiments if they have only the standard model (SM)-like left-handed vector couplings to gauge bosons. We discuss deviations from the confusion theorem in the presence of non-standard neutrino interactions, allowing to discover or constrain such novel couplings. We illustrate the general results with two chosen examples of neutral current processes, $Z \to ν\, \overlineν$ and $\mathcal{P}_i \to \mathcal{P}_f \, ν\, \overlineν$ (with $\mathcal{P}_{i,f}$ denoting pseudoscalar mesons, such as $B,K,π$). Our analysis shows that using 3-body decays the presence of non-standard interactions can not only be constrained but one can also distinguish between Dirac and Majorana neutrino possibilities.

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arXiv2020

Analytical description of CP violation in oscillations of atmospheric neutrinos traversing the Earth

Flavour oscillations of sub-GeV atmospheric neutrinos and antineutrinos, traversing different distances inside the Earth, are a promising source of information on the leptonic CP phase $δ$. In that energy range, the oscillations are very fast, far beyond the resolution of modern neutrino detectors. However, the necessary averaging over the experimentally typical energy and azimuthal angle bins does not wash out the CP violation effects. In this paper we derive very accurate analytic compact expressions for the averaged oscillations probabilities. Assuming spherically symmetric Earth, the averaged oscillation probabilities are described in terms of two analytically calculable effective parameters. Based on those expressions, we estimate maximal magnitude of CP-violation effects in such measurements and propose optimal observables best suited to determine the value of the CP phase in the PMNS mixing matrix.

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arXiv2019

Proposal for the validation of Monte Carlo implementations of the standard model effective field theory

We propose a procedure to cross-validate Monte Carlo implementations of the standard model effective field theory. It is based on the numerical comparison of squared amplitudes computed at specific phase-space and parameter points in pairs of implementations. Interactions are fully linearised in the effective field theory expansion. The squares of linear effective field theory amplitudes and their interference with standard-model contributions are compared separately. Such pairwise comparisons are primarily performed at tree level and a possible extension to the one-loop level is also briefly considered. We list the current standard model effective field theory implementations and the comparisons performed to date.

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arXiv2018

WCxf: an exchange format for Wilson coefficients beyond the Standard Model

We define a data exchange format for numerical values of Wilson coefficients of local operators parameterising low-energy effects of physics beyond the Standard Model. The format facilitates interfacing model-specific Wilson coefficient calculators, renormalisation group (RG) runners, and observable calculators. It is designed to be unambiguous (defining a non-redundant set of operators with fixed normalisation in each basis), extensible (allowing the addition of new EFTs or bases by the user), and robust (being based on industry standard file formats with parsers implemented in many programming languages). We have implemented the format for the Standard Model EFT (SMEFT) and for the weak effective theory (WET) below the electroweak scale and have added interfaces to a number of public codes dealing with SMEFT or WET. We also provide command-line utilities and a Python module for convenient manipulation of WCxf files, including translation between different bases and matching from SMEFT to WET.

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arXiv2018

Same-sign WW scattering at the LHC: can we discover BSM effects before discovering new states?

It is possible that measurements of vector boson scattering (VBS) at the LHC will reveal disagreement with Standard Model predictions, but no new particles will be observed directly. The task is then to learn as much as possible about the new physics from a VBS analysis carried within the framework of the Effective Field Theory (EFT). In this paper we discuss issues related to the correct usage of the EFT when the WW invariant mass is not directly accessible experimentally, as in purely leptonic W decay channels. The strategies for future data analyses in case such scenario indeed occurs are proposed.

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arXiv2018

Lepton flavour violation in the MSSM: exact diagonalization vs mass expansion

The forthcoming precision data on lepton flavour violating decays require precise and efficient calculations in New Physics models. In this article lepton flavour violating processes within the Minimal Supersymmetric Standard Model (MSSM) are calculated using the method based on the Flavour Expansion Theorem, a recently developed technique performing a purely algebraic mass-insertion expansion of the amplitudes. The expansion in both flavour-violating and flavour-conserving off-diagonal terms of sfermion and supersymmetric fermion mass matrices is considered. In this way the relevant processes are expressed directly in terms of the parameters of the MSSM Lagrangian. We also study the decoupling properties of the amplitudes. The results are compared to the corresponding calculations in the mass eigenbasis (i.e. using the exact diagonalization of the mass matrices). Using these methods, we consider the following processes: $\ell \to \ell' γ$, $\ell \to 3 \ell'$, $\ell \to 2\ell'\ell"$, $h \to \ell\ell'$ as well as $μ\to e$ conversion in nuclei. In the numerical analysis we update the bounds on the flavour changing parameters of the MSSM and examine the sensitivity to the forthcoming experimental results. We find that flavour violating muon decays provide the most stringent bounds on supersymmetric effects and will continue to do so in the future. Radiative $\ell\to\ell^\primeγ$ decays and leptonic three-body decays $\ell\to 3\ell^\prime$ show an interesting complementarity in eliminating "blind spots" in the parameter space. In our analysis we also include the effects of non-holomorphic $A$-terms which are important for the study of LFV Higgs decays.

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arXiv2017

General Mass Insertion Expansion in Flavor Physics

Calculating amplitudes for the flavor changing transitions in terms of the off-diagonal elements of mass matrices, so called "Mass Insertions" (MI) in the theory defined in "gauge basis" (before mass matrix diagonalization) is the common technique in analyzing the flavor structure of the New Physics models. I present a general method allowing to expand any QFT amplitude calculated in the mass-eigenstates (physical) basis into series in MI's, to any required order. The technique is purely algebraic, translating an amplitude written in the mass eigenbasis into MI series without performing diagrammatic calculations in the gauge basis. It can be applied for all types of mass matrices - either Hermitian (scalar or vector), general complex (Dirac fermions) or complex symmetric (Majorana fermions). Proposed expansion has been also automatized in the form of publicly available specialized Mathematica package, MassToMI, which features I illustrate with the example of the Higgs boson decays in the MSSM.

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arXiv2015

MassToMI - a Mathematica package for an automatic Mass Insertion expansion

We present a Mathematica package designed to automatize the expansion of QFT transition amplitudes calculated in the mass eigenstates basis (i.e. expressed in terms of physical masses and mixing matrices) into series of "mass insertions", defined as off-diagonal entries of mass matrices in Lagrangian before diagonalization and identification of the physical states. The algorithm implemented in this package is based on the general "Flavor Expansion Theorem" proven in Ref.~\cite{FET}. The supplied routines are able to automatically analyze the structure of the amplitude, identify the parts which could be expanded and expand them to any required order. They are capable of dealing with amplitudes depending on both scalar or vector (Hermitian) and Dirac or Majorana fermion (complex) mass matrices. The package can be downloaded from the address www.fuw.edu.pl/masstomi.

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arXiv2015

Lepton-flavour violating $B$ decays in generic $Z^\prime$ models

LHCb has reported deviations from the Standard Model in $b\to sμ^+μ^-$ transitions for which a new neutral gauge boson is a prime candidate for an explanation. As this gauge boson has to couple in a flavour non-universal way to muons and electrons in order to explain $R_K$, it is interesting to examine the possibility that also lepton flavour is violated, especially in the light of the CMS excess in $h\toτ^\pmμ^\mp$. In this article, we investigate the perspectives to discover the lepton-flavour violating modes $B\to K^{(*)}τ^\pmμ^\mp$, $B_s\to τ^\pmμ^\mp$ and $B\to K^{(*)} μ^\pm e^\mp$, $B_s\to μ^\pm e^\mp$. For this purpose we consider a simplified model in which new-physics effects originate from an additional neutral gauge boson ($Z^\prime$) with generic couplings to quarks and leptons. The constraints from $τ\to3μ$, $τ\toμν\barν$, $μ\to eγ$, $g_μ-2$, semi-leptonic $b\to sμ^+μ^-$ decays, $B\to K^{(*)}νν$ and $B_s$--$\overline{B}_s$ mixing are examined. From these decays, we determine upper bounds on the decay rates of lepton flavour violating $B$ decays. $Br(B\to Kνν)$ limits the branching ratios of LFV $B$ decays to be smaller than $8\times 10^{-5} (2\times 10^{-5})$ for vectorial (left-handed) lepton couplings. However, much stronger bounds can be obtained by a combined analysis of $B_s$--$\overline{B}_s$, $τ\to3μ$, $τ\toμν\barν$ and other rare decays. The bounds depend on the amount of fine-tuning among the contributions to $B_s$--$\overline{B}_s$ mixing. Allowing for a fine-tuning at the percent level we find upper bounds of the order of $10^{-6}$ for branching ratios into $τμ$ final states, while $B_s\to μ^\pm e^\mp$ is strongly suppressed and only $B\to K^{(*)} μ^\pm e^\mp$ can be experimentally accessible (with a branching ratio of order $10^{-7}$).

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arXiv2014

SUSY FLAVOR v2.5: a computational tool for FCNC and CP-violating processes in the MSSM

We present SUSY_FLAVOR version 2.5 - program that calculates over 30 low-energy flavor observables in the general $R$-parity conserving MSSM. Comparing to previous versions, in SUSY_FLAVOR v2.5 parameter initialization in SLHA2 formats has been significantly generalized, so that the program accepts most of the output files produced by other libraries analyzing the MSSM phenomenology. Number of bugs and inconsistencies have been fixed, based on users feedback. Calculations of several processes implemented in earlier versions have been corrected. New processes of rare decays of the top quark to Higgs boson have been included. Variables controlling inclusion of contributions from various MSSM sectors have been added. Full updated manual of SUSY_FLAVOR v2.5 integrating the details of the modifications listed below can be found at {\tt arxiv.org/abs/arXiv:1203.5023}.

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arXiv2014

Lepton Flavor Violation in the Standard Model with general Dimension-Six Operators

We study lepton flavor observables in the Standard Model (SM) extended with all dimension-$6$ operators which are invariant under the SM gauge group. We calculate the complete one-loop predictions to the radiative lepton decays $μ\to eγ$, $τ\to μγ$ and $τ\to eγ$ as well as to the closely related anomalous magnetic moments and electric dipole moments of charged leptons, taking into account all dimension-$6$ operators which can generate lepton flavor violation. Also the 3-body flavor violating charged lepton decays $τ^\pm \to μ^\pm μ^+ μ^-$, $τ^\pm\to e^\pm e^+ e^- $, $τ^\pm \to e^\pm μ^+ μ^- $, $τ^\pm \to μ^\pm e^+ e^- $, $τ^\pm \to e^\mp μ^\pm μ^\pm$, $τ^\pm \to μ^\mp e^\pm e^\pm $ and $μ^\pm \to e^\pm e^+ e^-$ and the $Z^0$ decays $Z^0\to\ell_i^+\ell_j^-$ are considered, taking into account all tree-level contributions.

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arXiv2013

SUSY_FLAVOR library for rare decays in the MSSM

SUSY_FLAVOUR 2.0 is a FORTRAN code calculating over 30 low-energy flavour- and CP-related observables in the R-parity conserving MSSM. The code admits for the most general flavour structure of the SUSY breaking terms and complex flavour-diagonal couplings. It includes the numerically important resummation of chirally enhanced effects and it is fast enough for scanning over a large SUSY-parameter space. The program can be obtained from http://www.fuw.edu.pl/susy_flavor.

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arXiv2013

Complete resummation of chirally-enhanced loop-effects in the MSSM with non-minimal sources of flavor-violation

In this article we present the complete resummation of the leading chirally-enhanced corrections stemming from gluino-squark, chargino-sfermion and neutralino-sfermion loops in the MSSM with non-minimal sources of flavor-violation. We compute the finite renormalization of fermion masses and the CKM matrix induced by chirality-flipping self-energies. In the decoupling limit Msusy>>v, which is an excellent approximation to the full theory, we give analytic results for the effective gaugino(higgsino)-fermion-sfermion and the Higgs-fermion-fermion vertices. Using these vertices as effective Feynman rules, all leading chirally-enhanced corrections can consistently be included into perturbative calculations of Feynman amplitudes. We also give a generalized parametrization for the bare CKM matrix which extends the classic Wolfenstein parametrization to the case of complex parameters lambda and A.

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arXiv2012

SUSY_FLAVOR library and constraints on $B_s \to μ^+ μ^-$ decay rate

I present SUSY_FLAVOR - a Fortran 77 program able to calculate simultaneously 29 low-energy flavor and CP-violating observables in the general R-parity conserving MSSM, including the case of large flavor violation in the sfermion sector. SUSY_FLAVOR v2 performs also the resummation of chirally enhanced corrections, arising in large $\tanβ$ regime and/or large trilinear soft mixing terms, to all orders of perturbation theory. I discuss an example of application of SUSY_FLAVOR to analysis of the $B_s \to μ^+ μ^-$ decay rate in the MSSM.

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