Non-standard Particles Research Articles

Theoretical concepts and measurement prospects for BSM trilinear couplings: a case study for scalar top quarks

After the possible discovery of new heavy particles at the LHC, it will be crucial to determine the properties and the underlying physics of the new states. In this work, we focus on scalar trilinear couplings, employing as an example the case of the trilinear coupling of scalar partners of the top quark to the Higgs boson. We discuss possible strategies for experimentally determining the scalar top (stop) trilinear coupling parameter, which controls the stop–stop–Higgs interaction, and we demonstrate the impact of different renormalisation prescriptions for this parameter. We find that the best prospects for determining the stop trilinear coupling arise from its quantum effects entering the model prediction for the mass of the SM-like Higgs boson in comparison to the measured value. We point out that the prediction for the Higgs-boson mass has a high sensitivity to the stop trilinear coupling even for heavy masses of the non-standard particles. Regarding the renormalisation of the stop trilinear coupling we identify a renormalisation scheme that is preferred in view of the present level of accuracy and we clarify the source of potentially large logarithms that cannot be resummed with standard renormalisation group methods.

Structure Formation of Concrete Systems Modified By Nonstandard Particles

The paper studies the matrix formation of the concrete mix modified by nonstandard particles introduced in the concentration of 0 ≤ k ≤ 0.5 in the initial composition of the dispersed phase. The development of the spatial functional groups in concrete dispersions is identified, which are filled with nonstandard particles with varying degrees. The addition of nonstandard particles to the concrete matrix composition leads to the formation of strong structural bonds due to the particle contacting via the adsorption and diffusion layers appearing during the formation of sub-microcrystalline gel surrounded by newly-formed dispersions (calcium silicate hydrates). This is because the high FeO content in the initial composition of nonstandard particles, which affects the particle adhesion in the dispersed phase. The latter possess the high electrostatic and electromagnetic attraction that generates crystallization centers on the contact surface of interphase boundaries.

Influence of non-standard particles on the concrete system matrix

This paper describes the influence of non-standard particles on the matrix of the concrete system. It is found that in the concrete dispersion systems, the formation and development of the spatial structures occurs with the different degree of their occupation with non-standard particles. The introduction of non-standard particles in the concrete matrix leads to the formation of strong structural bonds due to the particle interaction through the adsorption and diffusion layers. The latter appear during the formation of sub-microcrystalline helium surrounded by newly formed dispersion regions (C-S-H). The scanning electron microscopy is used to verify the formation of the structural bonds in the concrete system matrix.

Процессы структурообразования матриц бетонных систем, модифицированых некондиционными частицами

The paper presents theoretical and experimental results of the concrete matrix formation during the introduction of non-standard particles in the dispersion phase in the amount of 0 ≤ k ≥ 0.5. It is found that the space frame structures that appear and develop in concrete dispersion systems are occupied by the non-standard particles at varying degrees. The introduction of non-standard particles in the concrete matrix causes the formation of strong structural bonds due to the particle interaction via the adsorption and diffusion layers. The latter appear during the formation of sub-microcrystalline structure of helium covered with newly formed dispersion systems (C-S-H). This is because the high FeO content in the initial composition of non-standard particles that affects the particle bonding in the dispersion phase. The dispersion phase particles have the high electrostatic and electromagnetic attraction and form crystallization nuclei at the phase boundaries.

Flavourful axion phenomenology

We present a comprehensive discussion of the phenomenology of flavourful axions, including both standard Peccei-Quinn (PQ) axions, associated with the solution to the strong CP problem, and non-standard axion-like particles (ALPs). We give the flavourful axion-fermion and axion-photon couplings and calculate the branching ratios of heavy meson (K, D, B) decays involving a flavourful axion. We also calculate the mixing between axions and heavy mesons K0, D0, B0 and Bs0, which affects the meson oscillation probability and mass difference. Mixing also contributes to meson decays into axions and axion decays into two photons, and may be relevant for ALPs. We discuss charged lepton flavour-violating decays involving final state axions of the form ℓ1 → ℓ2a(γ), as well as μ → eee and μ − e conversion. Finally we describe the phenomenology of a particular “A to Z” Pati-Salam model, in which PQ symmetry arises accidentally due to discrete flavour symmetry. Here all axion couplings are fixed by a fit to flavour data, leading to sharp predictions and correlations between flavour-dependent observables.

Exploring X-ray lines as scotogenic signals

We consider some implications of X-ray lines from certain astronomical objects as potential effects of dark matter decay in the context of the scotogenic model, where neutrinos acquire mass radiatively via one-loop interactions with dark matter. As an example, we focus on the 3.5 keV line recently detected in the X-ray spectra of galaxy clusters, assuming that it stands future scrutiny. We explore the scenario in which the line originates from the slow decay of fermionic dark matter in the model. After obtaining a number of benchmark points representing the parameter space consistent with the new data and various other constraints, we make predictions on several observables in leptonic processes. They include the effective Majorana mass in neutrinoless double-beta decay, the sum of neutrino masses, and the rate of flavor-changing decay μ→eγ, as well as the cross sections of e+e− collisions into final states containing nonstandard particles in the model. These are testable in ongoing or future experiments and thus offer means to probe the scotogenic scenario studied.

Probing scotogenic effects ine+e−colliders

We explore the possibility of employing e+e- colliders to probe the scotogenic model, in which neutrinos get mass radiatively via one-loop interactions involving dark matter. Assuming the lightest one of the new particles in the model to be fermionic cold dark matter and taking into account various constraints, including those from LHC Higgs experiments, we show that LEP II data on e+e- scattering into a pair of charged leptons plus missing energy can place significant extra restrictions on the parameter space containing sufficiently low masses of the charged scalars in the model. On the other hand, LEP II data on e+e- collisions into a photon plus missing energy do not yield strong constraints. The allowed parameter space can still accommodate Higgs exotic decays into the nonstandard particles and thus is testable at the LHC. We also consider using future measurements of these two types of e+e- scattering at the International Linear Collider to examine the scenario of interest further and find that they can provide complementary information about it, whether or not they reveal scotogenic effects.

Probing scotogenic effects in Higgs boson decays

The recent observation of a Higgs boson at the LHC and experimental confirmation of the nonvanishing neutrino-mixing parameter $\mathrm{sin}{\ensuremath{\theta}}_{13}$ offer important means to test physics beyond the standard model. We explore this within the context of the scotogenic model, in which neutrinos acquire mass radiatively via one-loop interactions with dark matter. Starting with a two-parameter neutrino-mixing matrix which is consistent with the latest neutrino-oscillation data at the one-sigma level, we derive different sets of solutions for the Yukawa couplings of the nonstandard particles in the model and use the results to consider the Higgs decays into final states involving the new particles. Assuming that the lightest one of them serves as fermionic cold dark matter, we show that such decays are allowed by various experimental and theoretical constraints to have substantial rates that are already restricted by the current LHC data. We also look at their correlations with the Higgs decays into $\ensuremath{\gamma}\ensuremath{\gamma}$ and $\ensuremath{\gamma}Z$. Upcoming LHC measurements of the Higgs boson can therefore either detect scotogenic signals or place further constraints on the model.

New physics from ultrahigh energy cosmic rays

Cosmic rays from outer space enter the atmosphere with energies of up to ${10}^{11}\text{ }\text{ }\mathrm{GeV}$. The initial particle or a secondary hadron inside the shower may then interact with an air nucleon to produce nonstandard particles. In this article we study the production of new physics by high energy cosmic rays, focusing on the long-lived gluino of split-SUSY models and a weakly interacting massive particle (WIMP) working as dark matter. We first deduce the total flux of hadron events at any depth in the atmosphere, showing that secondary hadrons can not be neglected. Then we use these results to find the flux of gluinos and WIMPs that reach the ground after being produced inside air showers. We also evaluate the probability of producing these exotic particles in a single proton shower of ultrahigh energy. Finally we discuss the possible signal in current and projected experiments. While the tiny flux of WIMPs does not seem to have any phenomenological consequences, we show that the gluinos could modify substantially the profile of a small fraction of extensive air showers. In particular, they could produce a distinct signal observable at AUGER in showers of large zenith angle.

Muon (g-2): Renormalization at Work, All the Way Down to the Weak Scale

The anomalous magnetic moment of the muon, aµ, which is related to the spin g-factor by aµ =( gµ � 2)/2, has played a special role in the development of the standard model of particle physics. Because the anomaly of a point lepton results solely from radiative corrections, it has been at the center of the development of quantum electrodynamics, and of the standard model since the first observation of muon spin rotation and parity violation in muon decay. In the standard model, aµ has contributions from radiative corrections: from quantum electrodynamics; from strongly interacting particles in vacuum polarization loops with quantum numbers that couple to the photon; and from the electroweak gauge bosons. In principle, non-standard model particles could contribute as well, for example the supersymmetric partners of the electroweak bosons, if they exist. The history and the present status of both the theoretical and experimental values of the muon’s anomalous magnetic moment are reviewed.

Closing theSU(3)L⊗U(1)Xsymmetry at the electroweak scale

We show that some models with $SU(3)_C\otimes SU(3)_L\otimes U(1)_X$ gauge symmetry can be realized at the electroweak scale and that this is a consequence of an approximate global $SU(2)_{L+R}$ symmetry. This symmetry implies a condition among the vacuum expectation value of one of the neutral Higgs scalars, the $U(1)_X$'s coupling constant, $g_X$, the sine of the weak mixing angle $\sin\theta_W$, and the mass of the $W$ boson, $M_W$. In the limit in which this symmetry is valid it avoids the tree level mixing of the $Z$ boson of the Standard Model with the extra $Z^\prime$ boson. We have verified that the oblique $T$ parameter is within the allowed range indicating that the radiative corrections that induce such a mixing at the 1-loop level are small. We also show that a $SU(3)_{L+R}$ custodial symmetry implies that in some of the models we have to include sterile (singlets of the 3-3-1 symmetry) right-handed neutrinos with Majorana masses, being the see-saw mechanism mandatory to obtain light active neutrinos. Moreover, the approximate $SU(2)_{L+R}\subset SU(3)_{L+R}$ symmetry implies that the extra non-standard particles of these 3-3-1 models can be considerably lighter than it had been thought before so that new physics can be really just around the corner.

A SURVEY OF LATEST RESULTS FROM THE CDF EXPERIMENT

In 2001 the CDF experiment began a data-taking run at the highest centre-of-mass energies in the world. Expectations were high that this data would lead to an increased understanding of top physics and possible discovery of the Higgs boson and non-Standard Model particles. In this review we describe the aims and scope of this data-taking run, some of the upgrades carried out on CDF and our current experimental status. We briefly discuss the breadth of the CDF physics programme, before describing selected topics in quantum chromodynamics, heavy quark, electroweak and exotic physics. Latest results and projected ultimate experimental reach will be shown.

Flavour and model-independent Higgs boson searches at LEP

Now the LEP experiments have finalized their results on the Standard-Model Higgs boson, and are finalizing results on the most common Supersymmetric scenari, a wealth of results are being released that do not rely on explicit model assumptions, but rather on particular final states. In the absence of any convincing excess in the data, results are then extracted in a quasi model-independent way, most often in the form of excluded signal cross-sections, normalized to Standard Model cross-sections. The aim of the experiments is to provide a catalog of results that can be used in a straightforward way for future studies of models of electroweak symmetry breaking. PACS: 13.66.Fg Gauge and Higgs boson production in e+e– intteractions – 13.66.Hk Production of non-standard model particles in e+e– interactions

Search for excited fermions

Recent results on searches for excited fermions at the LEP, HERA and Tevatron colliders are reported. These results improve the limits on the masses and couplings of excited fermions. PACS: 12.60.Rc Composite models – 12.60.Cn Extensions of electroweak gauge sector – 13.66.Hk Production of non-standard model particles in e–e+ interactions – 13.60.Hb Total and inclusive cross sections (including deep-inelastic processes) – 13.85.Rm Limits on production of particles

Higgs boson decay into hadronic jets

The remarkable agreement of electroweak data with standard model (SM) predictions motivates the study of extensions of the SM in which the Higgs boson is light and couples in a standard way to the weak gauge bosons. Postulated new light particles should have small couplings to the gauge bosons. Within this context it is natural to assume that the branching fractions of the light SM-like Higgs boson mimic those in the standard model. This assumption may be unwarranted, however, if there are nonstandard light particles coupled weakly to the gauge bosons but strongly to the Higgs field. In particular, the Higgs boson may effectively decay into hadronic jets, possibly without important bottom or charm flavor content. As an example, we present a simple extension of the SM, in which the predominant decay of the Higgs boson occurs into a pair of light bottom squarks that, in turn, manifest themselves as hadronic jets. Discovery of the Higgs boson remains possible at an electron-positron linear collider, but prospects at hadron colliders are diminished substantially.

QCD radiation off heavy particles

We study QCD radiation in decay processes involving heavy particles. As input, the first-order gluon emission rate is calculated in a number of reactions, and comparisons of the energy flow patterns show a non-negligible process dependence. To proceed further, the QCD parton shower language offers a convenient approach to include multi-gluon emission effects, and to describe exclusive event properties. An existing shower algorithm is extended to take into account the process-dependent mass, spin and parity effects, as given by the matrix element calculations. This allows an improved description of multiple gluon emission effects off b and t quarks, and also off nonstandard particles like squarks and gluinos. Phenomenological applications are presented for bottom production at LEP, Higgs particle decay to heavy flavours, top production and decay at linear colliders, and some simple supersymmetric processes.

The Higgs sector of the MSSM in the decoupling limit

We study the heavy Higgs sector of the MSSM composed of the H^\pm, H^0 and A^0 particles in the so-called decoupling limit where m_{A^0} >> m_Z. By integrating out these heavy Higgs particles to one-loop, we compute the effective action for the electroweak gauge bosons and find out that, in the decoupling limit, all the heavy Higgs effects can be absorbed into redefinitions of the Standard Model electroweak parameters. This demonstrates explicitely that the decoupling theorem works for the heavy MSSM Higgs particles. This is also compared with the paradigmatic and different case of the Standard Model heavy Higgs particle. Finally, this work together with our two previous works, complete the demonstration that all the non-standard particles in the MSSM, namely, squarks, sleptons, charginos, neutralinos and the heavy Higgs particles, decouple to one-loop from the low energy electroweak gauge boson physics.

A realistic technicolor model from 150 TeV down

A realistic technicolor model is presented with the dynamics below 150 TeV treated explicitly. Electroweak symmetry is broken by the condensates of a “minimal” doublet of technifermions. The new feature of the model is that the third generation quarks are unified with the technifermions into multiplets of a walking gauge force down to a scale of 10 TeV. The remaining quarks and leptons are not involved in this unification however. The walking dynamics enhances the higher dimension interactions which give the ordinary fermions their masses and mixing, while leaving flavor-changing neutral currents suppressed. Because the third generation quarks actually feel the walking force their masses can be much larger than those of the other quarks and the leptons. The only non-standard particles with masses below several TeV are the single doublet of technifermions, so electroweak radiative corrections are estimable and within experimental limits. The tuning of couplings is mild.

Non-standard fermions at LEP

Many theoretical schemes predict the existence of unconventional quarks and leptons not fitting the standard pattern of fermion families. We consider two possible kinds of non-standard fermions, mirror fermions and exceptional fermions. Mirror fermions arise in a variety of models ranging from family unification to extended supersymmetry and Kaluza-Klein theories; exceptional fermions come along with the groupE 6 which is believed to be the low energy gauge symmetry of the superstring theory. We discuss some physical properties of these non-standard particles relevant for the LEP