PANCHTATAVAS - MYSTERIOUS WORLD OF MATTER

According to Ancient Indian philospers all matter of this universe is made up of five basic constituents commonly called panch tatavas. Indian philospher Maharishi Kanad around 500 BC postulated that matter is divisible. The smallest indivisible matter were named as parmanu. Greek philosphers named this indivisible particles atoms. In 1808 John Dalton suggest that the atom was indivisible and industructible. After the discovery of electron and proton inside the atom, led to the failure of Daltons theory. In the thirty years between the discovery of neutron in 1932 to the middle of 1962, more than thirty new particles were found, which were thought to be the builders of matter in the universe. Therefore it was established beyond doubt that all the particles discovered are not fundamental but have complex nature. In 1964 Gell-Mann and Zweing proposed that most of these particles called Quarks. Nearly 200 elementary particles were discovered so far. It appears that our search for the ultimate builder is not in a concluding stage but we are reaching towards the goal in stages. In this way we can say that the mysterious world of elementary particles and Quark is still mysterious. The same is written in Vedas and Purana that the search of ultimate particle will go on and on.

Search for new particles in events with energetic jets and large missing transverse momentum in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV

A search is presented for new particles produced at the LHC in proton-proton collisions at $$ \sqrt{s} $$ s = 13 TeV, using events with energetic jets and large missing transverse momentum. The analysis is based on a data sample corresponding to an integrated luminosity of 101 fb−1, collected in 2017–2018 with the CMS detector. Machine learning techniques are used to define separate categories for events with narrow jets from initial-state radiation and events with large-radius jets consistent with a hadronic decay of a W or Z boson. A statistical combination is made with an earlier search based on a data sample of 36 fb−1, collected in 2016. No significant excess of events is observed with respect to the standard model background expectation determined from control samples in data. The results are interpreted in terms of limits on the branching fraction of an invisible decay of the Higgs boson, as well as constraints on simplified models of dark matter, on first-generation scalar leptoquarks decaying to quarks and neutrinos, and on models with large extra dimensions. Several of the new limits, specifically for spin-1 dark matter mediators, pseudoscalar mediators, colored mediators, and leptoquarks, are the most restrictive to date.

Direct discovery of new light states at the FCCee

Light new states are ubiquitous in many models that address fundamental outstanding questions within the standard model (SM). The FCCee provides an excellent opportunity to probe these new particles with masses between 1 and $$100\,$$ 100 GeV and their electroweak couplings. Here we discuss the theory motivations for axion-like particles and heavy neutral leptons and detail the potential of direct discovery at the FCCee. We highlight that our current understanding requires light new states to be embedded within a bigger theory framework and thus the complementarity of the precision frontier at the FCCee and the high energy frontier of the FCChh program.

Consequences of chirally enhanced explanations of (g − 2)μ for h → μμ and Z → μμ

With the long-standing tension between experiment and Standard-Model (SM) prediction in the anomalous magnetic moment of the muon aμ recently reaffirmed by the Fermilab experiment, the crucial question becomes which other observables could be sensitive to the underlying physics beyond the SM to which aμ may be pointing. While from the effective field theory (EFT) point of view no direct correlations exist, this changes in specific new physics models. In particular, in the case of explanations involving heavy new particles above the electroweak (EW) scale with chiral enhancement, which are preferred to evade exclusion limits from direct searches, correlations with other observables sensitive to EW symmetry breaking are expected. Such scenarios can be classified according to the SU(2)L representations and the hypercharges of the new particles. We match the resulting class of models with heavy new scalars and fermions onto SMEFT and study the resulting correlations with h → μμ and Z → μμ decays, where, via SU(2)L symmetry, the latter process is related to Z → νν and modified W-μ-ν couplings.

ALP — SMEFT interference

The Standard Model Effective Field Theory (SMEFT) offers a powerful theoretical framework for parameterizing the low-energy effects of heavy new particles with masses far above the scale of electroweak symmetry breaking. Additional light degrees of freedom extend the effective theory. We show that light new particles that are weakly coupled to the SM via non-renormalizable interactions induce non-zero Wilson coefficients in the SMEFT Lagrangian via renormalization-group evolution. For the well-motivated example of axions and axion-like particles (ALPs) interacting with the SM via classically shift-invariant dimension-5 interactions, we calculate how these interactions contribute to the one-loop renormalization of the dimension-6 SMEFT operators, and how this running sources additional contributions to the Wilson coefficients on top of those expected from heavy new states. As an application, we study the ALP contributions to the magnetic dipole moment of the top quark and comment on implications of electroweak precision constraints on ALP couplings.

Naturalness without new particles

We demonstrate that the physics which resolves naturalness problems need not take the form of new particles and can sometimes manifest itself as higher dimensional operators. As a proof of principle, we present a simple model where the scale of new particles is parametrically separated from that estimated via naturalness arguments applied to self-quartic couplings. In this example, new particles appear far above the scale $$ m/\sqrt{\lambda } $$ m / λ , where m is the mass of the particle and λ is its self-quartic coupling. The shift symmetry responsible for resolving the naturalness problem involves higher dimensional operators rather than new particles.

Impacts of coagulation on the appearance time method for new particle growth rate evaluation and their corrections

The growth rate of atmospheric new particles is a key parameter that determines their survival probability of becoming cloud condensation nuclei and hence their impact on the climate. There have been several methods to estimate the new particle growth rate. However, due to the impact of coagulation and measurement uncertainties, it is still challenging to estimate the initial growth rate of new particles, especially in polluted environments with high background aerosol concentrations. In this study, we explore the influences of coagulation on the appearance time method to estimate the growth rate of sub-3 nm particles. The principle of the appearance time method and the impacts of coagulation on the retrieved growth rate are clarified via derivations. New formulae in both discrete and continuous spaces are proposed to correct for the impacts of coagulation. Aerosol dynamic models are used to test the new formulae. New particle formation in urban Beijing is used to illustrate the importance of considering the impacts of coagulation on the sub-3 nm particle growth rate and its calculation. We show that the conventional appearance time method needs to be corrected when the impacts of coagulation sink, coagulation source, and particle coagulation growth are non-negligible compared to the condensation growth. Under the simulation conditions with a constant concentration of non-volatile vapors, the corrected growth rate agrees with the theoretical growth rates. However, the uncorrected parameters, e.g., vapor evaporation and the variation in vapor concentration, may impact the growth rate obtained with the appearance time method. Under the simulation conditions with a varying vapor concentration, the average bias in the corrected 1.5–3 nm particle growth rate ranges from 6 %–44 %, and the maximum bias in the size-dependent growth rate is 150 %. During the test new particle formation event in urban Beijing, the corrected condensation growth rate of sub-3 nm particles was in accordance with the growth rate contributed by sulfuric acid condensation, whereas the conventional appearance time method overestimated the condensation growth rate of 1.5 nm particles by 80 %.

Increased new particle yields with largely decreased probability of survival to CCN size at the summit of Mt. Tai under reduced SO₂ emissions

Because anthropogenic sulfur dioxide (SO2) emissions have decreased considerably in the last decade, PM2.5 pollution in China has been alleviated to some extent. However, the effects of reduced SO2 on the particle number concentrations and subsequent contributions of grown new particles to cloud condensation nuclei (CCN) populations, particularly at high altitudes with low aerosol number loadings, are poorly understood. In contrast, the increase in provincial forest areas in China with rapid afforestation over the last few decades expectedly increases the biogenic emissions of volatile organic compounds and their oxidized products as nucleating precursors therein. In this study, we evaluated the campaign-based measurements made at the summit of Mt. Tai (1534 m a.s.l.) from 2007 to 2018. With the decrease in SO2 mixing ratios from 15 ± 13 ppb in 2007 to 1.6 ± 1.6 ppb in 2018, the apparent formation rate (FR) of new particles and the net maximum increase in the nucleation-mode particle number concentration (NMINP) in the spring campaign of 2018 was 2- to 3-fold higher than those in the spring campaign of 2007 with almost the same occurrence frequency of new particle formation (NPF) events. In contrast, the campaign-based comparison showed that the occurrence frequency, in which the maximum geometric median diameter of the grown new particles (Dpgmax) was > 50 nm, decreased considerably from 43 %–78 % of the NPF events before 2015 to < 12 % in 2017–2018. Assuming > 50 nm as a CCN threshold size at high supersaturations, the observed net CCN production decreased from 3.7 × 103 cm−3 (on average) in the five campaigns before 2015 to 1.0 × 103 cm−3 (on average) in the two campaigns in 2017–2018. We argue that the increases in the apparent FR and NMINP are mainly determined by the availability of organic precursors that participate in nucleation and initial growth, whereas the decrease in the growth probability is caused by the reduced emissions of anthropogenic precursors. However, large uncertainties still exist because of a lack of data on the chemical composition of these smaller particles.

Decay of standard model-like Higgs boson H_1→Z_γ in the simplest 3-3-1 model

The decays of the Higgs boson H_1→Z_γ are discussed in the simplest 3-3-1 model. Analytic formulas for one-loop contributions were constructed using well-known general results. We will show that new particles predicted by this simplest 3-3-1 model may gice significant effects to this decay of the standard model-like Higgs boson. From numerical investigation, some details and properties of this decay are presented. the may be useful for comparing with the experimental results that will be detected in the future.