Main Decay Modes Research Articles

Search for a light-charged Higgs in a two-Higgs-doublet type II seesaw model at the LHC

A charged Higgs in the type II two-Higgs-doublet model (THDM) has been bounded to be above a few hundred GeV by the radiative B decays. A Higgs triplet extension of the THDM not only provides an origin of neutrino masses and a completely new doubly-charged Higgs decay pattern, but it also achieves a light-charged Higgs with a mass of O(100) GeV through the new scalar couplings in the scalar potential. It was found that these light-charged Higgs decays depend on its mass mH±, tan⁡β, and mixing effect sin⁡θ±: at tan⁡β=1, if mH±>mW+mZ, b¯bW±, W±Z, and τν are the main decay modes; however, if mH±<mW+mZ, the main decay modes are then b¯bW and τν, and at tan⁡β=30, the τν mode dominates the other decays. When mt>mH±+mb, we found that the ATLAS and CMS recent upper bounds on the product of BR(t→H+b)BR(H+→τ+ν) can be directly applied and will give a strict constraint on the correlation of mH± and sin⁡θ±. If the upper bound of BR(t→H+b)BR(H+→τ+ν) is satisfied (escaped) for mt>(<)mH±+mb, it was found that the significance of discovering the charged Higgs through H±→W±Z is much lower than that through H±→b¯bW±. With a luminosity of 100 fb−1 at s=13 TeV and including the experimental bounds, the significance of the H±→b¯bW± signal can reach around 6.2(2.4)σ for mH±<(>)mW+mZ.

Flavor changing nucleon decay

Recent discovery of neutrino large mixings implies the large mixings in the diagonalizing matrices of 5¯ fields in SU(5) grand unified theory (GUT), while the diagonalizing matrices of 10 fields of SU(5) are expected to have small mixings like Cabibbo–Kobayashi–Maskawa matrix. We calculate the predictions of flavor changing nucleon decays (FCND) in SU(5), SO(10), and E6 GUT models which have the above features for mixings. We found that FCND can be the main decay mode and play an important role to test GUT models.

Formation and decay of the compound nucleus Th*220 within the dynamical cluster-decay model

Background: The radioactive $^{220}\mathrm{Th}^{*}$ compound nucleus (CN) is of interest since the evaporation residue (ER) cross sections are available for various entrance channels $^{16}\mathrm{O}+^{204}\mathrm{Pb}$, $^{40}\mathrm{Ar}+^{180}\mathrm{Hf}$, $^{48}\mathrm{Ca}+^{172}\mathrm{Yb}$, and $^{82}\mathrm{Se}+^{138}\mathrm{Ba}$ at near barrier energies. Within the dynamical cluster-decay model (DCM), the radioactive CNs $^{215}\mathrm{Fr}^{*}$, $^{242}\mathrm{Pu}^{*}$, $^{246}\mathrm{Bk}^{*}$, and $^{254}\mathrm{Fm}^{*}$ are studied where the main decay mode is fission, with very small predicted ER cross section. $^{220}\mathrm{Th}^{*}$ provides a first case with experimentally observed ER cross section instead of fission.Purpose: To look for the optimum ``hot-compact'' target-projectile (t-p) combinations for the synthesis of ``cold'' $^{220}\mathrm{Th}^{*}$ and then its decay. For best fitting of the measured ER cross sections, with quasifission (qf) content, if any, the fusion-fission (ff) component is predicted. The magic-shell structure and entrance channel mass-asymmetry effects are analyzed, and the behavior of CN formation and survival probabilities ${P}_{\mathrm{CN}}$ and ${P}_{\mathrm{surv}}$ is studied.Methods: The quantum-mechanical fragmentation theory (QMFT) is used to predict the possible cold t-p combinations for synthesizing $^{220}\mathrm{Th}^{*}$, and the QMFT-based DCM is used to analyze its decay channels for the experimentally studied entrance channels. The only parameter of the model, the neck length $\mathrm{\ensuremath{\Delta}}R$, varies smoothly with the excitation energy ${E}^{*}$ of CN and is used to best fit the ER data and predict qf and ff cross sections.Results: The hot-compact and ``cold-elongated'' fragmentation paths show dissimilar results, whose comparisons with measured fission yields result in t-p combinations, the cold reaction valleys. For the decay process, the fixed $\mathrm{\ensuremath{\Delta}}R$ fit the measured ER cross section nicely, but not the individual decay-channel cross sections, which require the presence of qf effects, less so for asymmetric t-p combinations, and large (predicted) ff cross section.Conclusions: The calculated yields for hot-compact fragmentation path compared favorably with the observed asymmetric fission-mass distribution, resulting in mostly the same t-p reactions as are used in experiments. The best fitted $\mathrm{\ensuremath{\Delta}}R$ are found to be independent of the entrance channels, despite their very different cross sections, in conformity with our earlier works. The entrance-channel effects lead to the largest decay cross section for the most asymmetric and doubly magic t-p combination, the magicity taking over asymmetry for both the total ER and channel cross section. Furthermore, the variation of both ${P}_{\mathrm{CN}}$ and ${P}_{\mathrm{surv}}$ with ${E}^{*}$ fit in with the known systematic of other radioactive CN studied so far, thereby giving credence to our DCM analysis of $^{220}\mathrm{Th}^{*}$.

Competition between α decay and proton radioactivity of neutron-deficient nuclei

The $\ensuremath{\alpha}$ decay and proton radioactivity half-lives of some neutron-deficient nuclei are calculated using an effective liquid drop model (ELDM). It is found that the experimental half-lives of the two decay modes and the dominant decay mode can be well reproduced by the ELDM. Moreover, the predicted penetration probabilities ($P$) of proton radioactivity by the ELDM are in agreement with those by a microscopic model (MM). This allows us to make predictions on the competition of the two decay modes for nuclei whose experimental data are not available, which are useful for future measurements. In addition, the comparison between the predicted reduced proton radioactivity half-lives by the ELDM and the ones by a standard formula suggests that one is unlikely to observe large angular momentum transfers for nuclei with a very large Coulomb parameter $\ensuremath{\chi}$. Last, we find that in most isotope chains the proton radioactivity is the dominant decay mode for nuclei that are very close to the proton drip line. But with increasing neutron number $N$ the main decay mode is changed into $\ensuremath{\alpha}$ decay. With the decay energies the decay mode anomaly of $^{184}\mathrm{Bi}$ is discussed.

Charged Higgs Analysis in CMS

An overview is given of the possible searches of the Charged Higgs Boson during run 2 of the LHC data taking period. The Charged Higgs boson emerges in several (minimal) Standard Model (SM) extensions such as the 2 Doublet Higgs Model, which predicts 5 physical Higgs bosons, consistent with the SM Higgs boson. Based on the main production and decay modes, the possible intermediate and final state particles are predicted for a Charged Higgs mass higher than the top quark mass (mH± > mt). In particular, the dominant H±→τν to tau nu and H±→tb channels are discussed in more detail together with their associated background.

Ultrafast x-ray-induced nuclear dynamics in diatomic molecules using femtosecond x-ray-pump–x-ray-probe spectroscopy

The capability of generating two intense, femtosecond x-ray pulses with controlled time delay opens the possibility of performing time-resolved experiments for x-ray induced phenomena. We have applied this capability to study the photoinduced dynamics in diatomic molecules. In molecules composed of low-Z elements, \textit{K}-shell ionization creates a core-hole state in which the main decay mode is an Auger process involving two electrons in the valence shell. After Auger decay, the nuclear wavepackets of the transient two-valence-hole states continue evolving on the femtosecond timescale, leading either to separated atomic ions or long-lived quasi-bound states. By using an x-ray pump and an x-ray probe pulse tuned above the \textit{K}-shell ionization threshold of the nitrogen molecule, we are able to observe ion dissociation in progress by measuring the time-dependent kinetic energy releases of different breakup channels. We simulated the measurements on N$_2$ with a molecular dynamics model that accounts for \textit{K}-shell ionization, Auger decay, and the time evolution of the nuclear wavepackets. In addition to explaining the time-dependent feature in the measured kinetic energy release distributions from the dissociative states, the simulation also reveals the contributions of quasi-bound states.

Prospects for spin-1 resonance search at 13 TeV LHC and the ATLAS diboson excess

Motivated by ATLAS diboson excess around 2 TeV, we investigate a phenomenology of spin-1 resonances in a model where electroweak sector in the SM is weakly coupled to strong dynamics. The spin-1 resonances, W' and Z', are introduced as effective degrees of freedom of the dynamical sector. We explore several theoretical constraints by investigating the scalar potential of the model as well as the current bounds from the LHC and precision measurements. It is found that the main decay modes are V' -> VV and V' -> Vh, and the V' width is narrow enough so that the ATLAS diboson excess can be explained. In order to investigate future prospects, we also perform collider simulations at the 13 TeV LHC, and obtain a model independent expected exclusion limit for the process pp -> W' -> WZ -> JJ. We find a parameter space where the diboson excess can be explained, and are within a reach of the LHC at the integrated luminosity of 10 fb-1 and 13 TeV.

Doubly charged Higgs bosons pair production through WW fusion at high-energy e+e− linear colliders

The doubly charged Higgs bosons are the typical particles predicted in the Higgs triplet model (HTM), and the detection of them is a key to probe this model. In this letter, we focus on the study of the doubly charged Higgs bosons pair production through WW fusion process: . We calculate the production cross-sections and compare the results with those in the s-channel pair production process: . The final signals and the relevant SM backgrounds are also examined based on two main decay modes of : and (). Our numerical results show that, the possible signals of might be observed via this process in future high-energy linear-collider experiments.

Spin density matrix of the $$\omega $$ ω in the reaction $${\bar{p}p}\,\rightarrow \,\omega \pi ^0$$ p ¯ p → ω π 0

The spin density matrix of the \(\omega \) has been determined for the reaction \({\bar{p}p}\,\rightarrow \,\omega \pi ^0\) with unpolarized in-flight data measured by the Crystal Barrel LEAR experiment at CERN. The two main decay modes of the \(\omega \) into \(\pi ^0 \gamma \) and \(\pi ^+ \pi ^- \pi ^0\) have been separately analyzed for various \({\bar{p}}\)momenta between 600 and 1940 MeV/c. The results obtained with the usual method by extracting the matrix elements via the \(\omega \) decay angular distributions and with the more sophisticated method via a full partial wave analysis are in good agreement. A strong spin alignment of the \(\omega \) is clearly visible in this energy regime and all individual spin density matrix elements exhibit an oscillatory dependence on the production angle. In addition, the largest contributing orbital angular momentum of the \({\bar{p}p~}\)system has been identified for the different beam momenta. It increases from \(L^{max}_{{\bar{p}p~}}\) \(=\) 2 at 600 MeV/c to \(L^{max}_{{\bar{p}p~}}\) \(=\) 5 at 1940 MeV/c.

Review of physics results from the Tevatron: Higgs boson physics

We review the techniques and results of the searches for the Higgs boson performed by the two Tevatron collaborations, CDF and DØ. The Higgs boson predicted by the Standard Model was sought in the mass range 90 GeV &lt; mH &lt; 200 GeV in all main production modes at the Tevatron: gluon–gluon fusion, WH and ZH associated production, vector boson fusion, and [Formula: see text] production, and in five main decay modes: [Formula: see text], H→τ+τ-, H→WW(*), H→ZZ(*) and H→γγ. An excess of events was seen in the [Formula: see text] searches consistent with a Standard Model Higgs boson with a mass in the range 115 GeV &lt; mH &lt; 135 GeV . Assuming a Higgs boson mass of mH = 125 GeV , studies of Higgs boson properties were performed, including measurements of the product of the cross section times the branching ratio in various production and decay modes, constraints on Higgs boson couplings to fermions and vector bosons, and tests of spin and parity. We also summarize the results of searches for supersymmetric Higgs bosons, and Higgs bosons in other extensions of the Standard Model.

$$D_{s1}^*(2860)$$ D s 1 ∗ ( 2860 ) and $$D_{s3}^*(2860)$$ D s 3 ∗ ( 2860 ) : candidates for $$1D$$ 1 D charmed-strange mesons

Newly observed two charmed-strange resonances, $D_{s1}^*(2860)$ and $D_{s3}^*(2860)$, are investigated by calculating their Okubo-Zweig-Iizuka allowed strong decays, which shows that they are suitable candidates for the $1^3D_1$ and $1^3D_3$ states in the charmed-strange meson family. Our study also predicts other main decay modes of $D_{s1}^*(2860)$ and $D_{s3}^*(2860)$, which can be accessible at the future experiment. In addition, the decay behaviors of the spin partners of $D_{s1}^*(2860)$ and $D_{s3}^*(2860)$, i.e., $1D(2^-)$ and $1D^\prime(2^-)$, are predicted in this work, which are still missing at present. Experimental search for the missing $1D(2^-)$ and $1D^\prime(2^-)$ charmed-strange mesons is an intriguing and challenging task for further experiment.

Sizeable beta-strength in 31Ar (β3p) decay

We present for the first time precise spectroscopic information on the recently discovered decay mode β-delayed 3p-emission. The detection of the 3p events gives an increased sensitivity to the high energy part of the Gamow–Teller strength distribution from the decay of 31Ar revealing that as much as 30% of the strength resides in the β3p-decay mode. A simplified description of how the main decay modes evolve as the excitation energy increases in 31Cl is provided.

The Higgs particle and higher-dimensional theories

In spite of the great success of LHC experiments, we do not know whether the discovered "standard model-like" Higgs particle is really what the standard model predicts or a particle some new physics has in its low energy effective theory. Also the long-standing problems concerning the property of Higgs and its interactions are still there, and we still do not have any conclusive argument of the origin of the Higgs itself. In this article we focus on higher-dimensional theories as new physics. First we give a brief review of their representative scenarios and closely related 4-dimensional scenarios. Among them, we mainly discuss two interesting possibilities of the origin of the Higgs: Higgs as a gauge boson and Higgs as a (pseudo) Nambu-Goldstone boson. Next, we argue that theories of new physics are divided into two categories, i.e. theories with normal Higgs interactions and those with anomalous Higgs interactions. Interestingly both of two candidates concerning the origin of the Higgs mentioned above predict characteristic "anomalous" Higgs interactions, such as the deviation of the Yukawa couplings from the standard model predictions. Such deviations can be hopefully investigated by the precision tests of Higgs interactions at the planned ILC experiment. Also discussed is the main decay mode of the Higgs, $H \to \gamma \gamma$. Again, theories belonging different categories are known to predict remarkably different new physics contributions to this important process.

Axial Crushes Simulation of Thin-walled Square Aluminum Alloy 6061-T5 Foam-filled Section

This paper deal with numerical study of the dynamic impact of axial crushing on thin-walled extrusion aluminum alloy 6061 and polystyrene foam-filled tubes square cross-section. Non-linear dynamic-impact simulation was done using finite element software's package as well on foam-filled model. Non-linear dynamic finite elements were carried out to simulate buckling and crushing phenomenon in the crushed event. Influence of fillers on the energy absorption behavior of square and thin-walled metal tube extrusion aluminum alloy 6061 estimates empty and foam-filled examined. Three main decay modes have been identified for the model is crushes, for example, diamond compound symmetry, axisymmetric concertina mode of formation and mixing times. Three different arrangement foam-filled inner tube columns has been examined and investigated.

Two-body strong decay of Z(3930) as the χ c2(2P) state

The new particle Z(3930) found by the Belle and BaBar Collaborations through the $\gamma\gamma\rightarrow D\bar D$ process is identified to be the $\chi_{c2}(2P)$ state. Since the mass of this particle is above the $D\bar D^{(\ast)}$ threshold, the OZI-allowed two-body strong decays are the main decay modes. In this paper, these strong decay modes are studied with two methods. One is the instantaneous Bethe-Salpeter method within Mandelstam formalism. The other is the combination of the $^3P_0$ model and the former formalism. The total decay widths are 26.3 and 27.3 MeV for the methods with or without the $^3P_0$ vertex, respectively. The ratio of $\Gamma_{D\bar D}$ over $\Gamma_{D\bar D^\ast}$ which changes along with the mass of the initial meson is also presented.

Direct constraints on the top-Higgs coupling from the 8 TeV LHC data

The LHC experiments have analyzed the 7 and 8 TeV LHC data in the main Higgs production and decay modes. Current analyses only loosely constrain an anomalous top-Higgs coupling in a direct way. In order to strongly constrain this coupling, the Higgs-top associated production is reanalyzed. Thanks to the strong destructive interference in the t-channel for standard model couplings, this process can be very sensitive to both the magnitude and the sign of a non-standard top-Higgs coupling. We project the sensitivity to anomalous couplings to the integrated luminosity of 50 fb^{-1}, corresponding to the data collected by the ATLAS and CMS experiments in 7 and 8 TeV collisions, as of 2012. We show that the combination of di-photon and multi-lepton signatures, originating from different combinations of the top and Higgs decay modes, can be a potential probe to constrain a large portion of the negative top-Higgs coupling space presently allowed by the ATLAS and CMS global fits.

Particle radioactivity of exotic nuclei

For the atomic nuclei located beyond the drip-lines, new forms of radioactivity are possible due to the instability against the emission of particles. At the neutron-deficient limit, single-proton and two-proton radioactivity are characteristic phenomena. While the former is well understood and represents a mature research field of nuclear spectroscopy, the knowledge about the latter is still scarce but growing rapidly. In some areas of the proton drip-line, α decay sets in as the main decay mode. This paper briefly describes the phenomena of particle emission at the proton drip-line and presents some examples illustrating the current status of experimental achievements and the theoretical understanding. The idea of the Gamow state as a unifying concept in the description of particle radioactivity is highlighted. The possibility for neutron radioactivity is briefly discussed.

DECAYS OF FOURTH GENERATION BOUND STATES

We consider the decay modes of the heavy [Formula: see text] bound states originating from Higgs boson exchange between quark–antiquark pair. In case of a small coupling between the fourth and lower generation the main decay mode is [Formula: see text] annihilation. We show that for a vector state the dominant decay modes are Higgs-gamma and Higgs-Z decays, while for a pseudoscalar state the strong two-gluon decay mode dominates. The bound states are very narrow. The ratio of the total width to the binding energy is less than 1% if we are not extremely close to the critical quark mass where the binding energy is very small. The discussed decay modes exist for any fermion–antifermion bound states including heavy leptons and heavy neutrinos if their masses are high enough to form a bound state due to attractive Higgs boson exchange potential.

Higgs physics: Theory

The theoretical aspects of the physics of Higgs bosons are reviewed focussing on the elements that are relevant for the production and detection at present hadron colliders. After briefly summarizing the basics of electroweak symmetry breaking in the Standard Model, the Higgs production at the LHC and at the Tevatron is discussed, with some focus on the main production mechanism, the gluon–gluon fusion process, and the main Higgs decay modes and the experimental detection channels are discussed. Then the case of the minimal supersymmetric extension of the Standard Model is briefly surveyed. In the last section, the prospects for determining the fundamental properties of the Higgs particles are reviewed, once they have been experimentally observed.

Radial excitation states of η and η′ in the chiral quark model

A chiral quark model is applied to calculate the spectra of pseudoscalar mesons η and η′. By analyzing the obtained spectra, we find that the mesons η′(21S0), η(41S0), η′(31S0) and η′(41S0) are the possible candidates of η(1760), X(1835), X(2120) and X(2370). The strong decay widths of these pseudoscalars to all the possible two-body decay channels are calculated within the framework of the 3P0 model. Although the total width of η′(21S0) is compatible with the BES Collaboration's experimental value for η(1760), the partial decay width to ωω is too small, which is not consistent with the BES result. If X(1835) is interpreted as η(41S0), the total decay width is compatible with the experimental data, and the main decay modes will be πa0(980) and πa0(1450), which needs to be checked experimentally. The assignment of X(2120) and X(2370) to η′(31S0) and η′(41S0) is disfavored in the present calculation because of the incompatibility of the decay widths.