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Kresimir Kumericki

Publications and source records attributed to Kresimir Kumericki.

At least 19 recordsLinked to original sources
arXiv2020

Separation of Quark Flavors using DVCS Data

Using the available data on deeply virtual Compton scattering (DVCS) off protons and utilizing neural networks enhanced by the dispersion relation constraint, we determine six out of eight leading Compton form factors in the valence quark kinematic region. Furthermore, adding recent data on DVCS off neutrons, we separate contributions of up and down quarks to the dominant form factor, thus paving the way towards a three-dimensional picture of the nucleon.

hep-ph↗
arXiv2017

Renormalizable SU(5) Completions of a Zee-type Neutrino Mass Model

We explore the potential of a selected model of radiative neutrino masses to be implemented in a renormalizable SU(5) unification framework. The Zee-type model under consideration uncovers the SU(5) representations in which the new fields are embedded and which may contain also other light states leading to the unification of gauge couplings. We perform an exhaustive search which reveals specific patterns of new states and demonstrate that such patterns are consistent with a general choice of relevant scalar potential. It turns out that all of the specific scenarios which lead to successful unification include the colored scalars testable at the LHC.

hep-ph↗
arXiv2017

Extended Higgs Sectors in Radiative Neutrino Models

Testable Higgs partners may be sought within the extensions of the SM Higgs sector aimed at generating neutrino masses at the loop level. We study a viability of extended Higgs sectors for two selected models of radiative neutrino masses: a one-loop mass model, providing the Higgs partner within a real triplet scalar representation, and a three-loop mass model, providing it within its two-Higgs-doublet sector. The Higgs sector in the one-loop model may remain stable and perturbative up to the Planck scale, whereas the three-loop model calls for a UV completion around 106 GeV. Additional vector-like lepton and exotic scalar fields, which are required to close one- and three-loop neutrino-mass diagrams, play a decisive role for the testability of the respective models. We constrain the parameter space of these models using LHC bounds on diboson resonances.

hep-ph↗
arXiv2017

Radiative neutrino models in light of diphoton signals

Viable explanations of a hinted 750 GeV scalar resonance may be sought within the extensions of the SM Higgs sector aimed at generating neutrino masses at the loop level. We confront a compatibility with the 750 GeV diphoton excess for two recent models which do not need to impose ad hoc symmetry to forbid the tree-level masses: a one-loop mass model providing the H(750) candidate within its real triplet scalar representation and a three-loop mass model providing it within its two Higgs doublets. Besides accounting for the 750 GeV resonance, we demonstrate that these complementary neutrino-mass scenarios have different testable predictions for the LHC which should show up soon as more data is accumulated during the ongoing 13 TeV run.

hep-ph↗
arXiv2016

Feynman Diagrams for Beginners

We give a short introduction to Feynman diagrams, with many exercises. Text is targeted at students who had little or no prior exposure to quantum field theory. We present condensed description of single-particle Dirac equation, free quantum fields and construction of Feynman amplitude using Feynman diagrams. As an example, we give a detailed calculation of cross-section for annihilation of electron and positron into a muon pair. We also show how such calculations are done with the aid of computer.

physics.ed-ph↗
arXiv2015

Scotogenic R\nuMDM at Three-Loop Level

We propose a model in which the radiative neutrino (Rν) masses are induced by fermion quintuplet and scalar septuplet fields from the minimal-dark-matter (MDM) setup. In conjunction with the 2HDM fields, on top of which our model is built, these hypercharge zero fields and additional scalar quintuplet lead to an accidental DM-protecting Z_2 symmetry and establish the R\nuMDM model at the three-loop level. We assess the potential for discovery of quintuplet fermions on present and future pp colliders.

hep-ph↗
arXiv2013

Deeply Virtual Compton Scattering at a Proposed High-Luminosity Electron-Ion Collider

Several observables for the deeply virtual Compton scattering process have been simulated in the kinematic regime of a proposed Electron-Ion Collider to explore the possible impact of such measurements for the phenomenological access of generalized parton distributions. In particular, emphasis is given to the transverse distribution of sea quarks and gluons and how such measurements can provide information on the angular momentum sum rule. The exact lepton energy loss dependence for the unpolarized $t$-differential electroproduction cross section, needed for a Rosenbluth separation, is also reported.

hep-ph↗
arXiv2013

Revealing CFFs and GPDs from experimental measurements

We report on the status of the phenomenological access of generalized parton distributions from photon and meson electroproduction off proton. Thereby, we emphasize the role of HERMES data for deeply virtual Compton scattering, which allows us to map various asymmetries into the space of Compton form factors.

hep-ph↗
arXiv2013

Neutrino Masses and TeV-scale Particles Testable at the LHC

We consider a scenario in which TeV-scale particles belonging to weak-isospin multiplets higher than triplets lead to novel seesaw mechanisms different from conventional type I, II and III seesaw models. Besides an appealing testability of these mechanisms at the LHC, the model with Majorana quintuplets with imposed discrete symmetry may provide viable dark matter candidate.

hep-ph↗
arXiv2013

HERMES impact for the access of Compton form factors

We utilize the DVCS asymmetry measurements of the HERMES collaboration for access to Compton form factors in the deeply virtual regime and to generalized parton distributions. In particular, the (almost) complete measurement of DVCS observables allows us to map various asymmetries into the space of Compton form factors, where we still rely in this analysis on dominance of twist-two associated Compton form factors. We compare this one-to-one map with local Compton form factor fits and a model dependent global fit.

hep-ph↗
arXiv2012

Critique of Fermionic R\nuMDM and its Scalar Variants

We examine the stability of minimal dark matter (MDM) particle-candidates in the setup in which they participate in radiative neutrino (Rν) masses. We first point out the existence of an additional renormalizable term in recently proposed R\nuMDM Lagrangian, which violates the claimed accidental Z_2 symmetry and spoils the stability of the fermionic MDM quintuplet component. We then explore the viability of R$ν$MDM variants based on scalar MDM multiplets. There are ubiquitous super-renormalizable terms in the scalar potential which make these scalar multiplets unstable.

hep-ph↗
arXiv2012

TeV-scale Seesaw with Quintuplet Fermions

We propose a new seesaw model based on fermionic hypercharge zero weak quintuplet in conjunction with additional scalar quadruplet which attains an induced vev. The model provides both tree-level seesaw ~ v^6/M^5 and a loop-suppressed radiative ~ (1 / 16 π^2) v^2/M contributions to active neutrino masses. The empirical masses m_ν~ 10^{-1} eV can be achieved with M ~ TeV new states, accessible at the LHC. For 5 fb^{-1} of accumulated integrated luminosity at the LHC, there could be ~ 500 doubly-charged Σ^{++} or \bar{Σ^{++}} fermions with mass M_Σ= 400 GeV, leading to interesting multi-lepton signatures. The neutral component of the fermion quintuplet, previously identified as minimal dark matter candidate, becomes unstable in the proposed seesaw setup. The stability can be restored by introducing a Z_2 symmetry, in which case neutrinos get mass only from radiative contributions.

hep-ph↗
arXiv2012

GPDs from present and future measurements

We report on the access of generalized parton distributions (GPDs) from deeply virtual Compton scattering (DVCS) measurements. We also point out that such measurements at a proposed high-luminosity electron-ion collider (EIC) provide insight in both the transverse distribution of sea quarks and gluons as well as the proton spin decomposition.

hep-ph↗
arXiv2011

Parametrizing Compton form factors with neural networks

We describe a method, based on neural networks, of revealing Compton form factors in the deeply virtual region. We compare this approach to standard least-squares model fitting both for a simplified toy case and for HERMES data.

hep-ph↗
arXiv2011

Exotic Seesaw-Motivated Heavy Leptons at the LHC

We study the LHC potential for discovering TeV-scale SU(2)_L 5-plet fermions introduced recently to explain small neutrino masses. We show that the Drell-Yan production and the decays of new exotic Sigma leptons are testable at the LHC. Their production is abundant due to nontrivial electroweak gauge charges. For 1 fb^-1 of integrated luminosity at the present LHC sqrt{s}=7 TeV, there can be 270 Sigma-Sigmabar pairs produced for M_Sigma = 400 GeV. Besides producing same-sign dilepton events, they could lead, due to a chosen small mixing between heavy and light leptons, to ~10 golden decays Sigma^{+++}(Sigma^{+++}-bar) --> W^\pm W^\pm l^\pm with a specific decay signature.

hep-ph↗
arXiv2011

Studying Deeply Virtual Compton Scattering with Neural Networks

Neural networks are utilized to fit Compton form factor H to HERMES data on deeply virtual Compton scattering off unpolarized protons. We used this result to predict the beam charge-spin assymetry for muon scattering off proton at the kinematics of the COMPASS II experiment.

hep-ph↗
arXiv2011

Neural network generated parametrizations of deeply virtual Compton form factors

We have generated a parametrization of the Compton form factor (CFF) H based on data from deeply virtual Compton scattering (DVCS) using neural networks. This approach offers an essentially model-independent fitting procedure, which provides realistic uncertainties. Furthermore, it facilitates propagation of uncertainties from experimental data to CFFs. We assumed dominance of the CFF H and used HERMES data on DVCS off unpolarized protons. We predict the beam charge-spin asymmetry for a proton at the kinematics of the COMPASS II experiment.

hep-ph↗