We study the morphology of the main drift chamber (MDC) to be built around the collision point of the proposed Super tau-charm facility (STCF), to check its suitability for discovering the 17 MeV protophobic boson (X17 boson), hypothesised as a solution to the persistent ATOMKI nuclear-transition anomalies. Using the TrackEff framework, we perform detector-level simulations of the STCF MDC, and evaluate displaced-vertex sensitivities towards the protophobic boson, across the relevant mass-coupling parameter space. We study benchmark scenarios with visible and dark decay channels to perform likelihood-based significance estimates in order to determine the 5 $\textit{σ}$ discovery reach for the protophobic boson. We find that STCF can potentially discover the protophobic boson while tolerating ~ 10 background events for specific regions of the parameter space. Our analysis establishes the first feasibility study of displaced light-boson searches at the STCF, motivating a full Geant-4 simulation.

India

Althaf M.

Triparno Bandyopadhyay

Potential for the discovery of the protophobic boson at the STCF

We present a framework of dark- and visible-sector unification in the E embedding of the standard model. The demand for consistently getting the standard model leads to the existence of the dark-sector. We show that the hierarchy of vevs typifying unified models leads to multicomponent dark matter at the IR. The symmetry breaking itself categorises the matter content into dark- and visible-sector particles, the categorisation being uniform across different breaking chains. We discuss the stability of the dark matter particles and compare them to existing phenomenological models of dark matter. The central results follow from symmetry and hierarchy arguments. We present an indicative set of models of gauge coupling unification, to show that the framework can be embedded in realistic models of E .

South Korea

Rinku Maji

The E

We propose a tantalizing possibility that misinterpretation of the reconstructed missing momentum may have yielded the observed discrepancies among measurements of the W-mass in different collider experiments. We introduce a proof-of-principle scenario characterized by a new physics particle, which can be produced associated with the W-boson in hadron collisions and contributes to the net missing momentum observed in a detector. We show that these exotic events pass the selection criteria imposed by various collaborations at reasonably high rates. Consequently, in the presence of even a handful of these events, a fit based on the ansatz that the missing momentum is primarily due to neutrinos (as it happens in the Standard Model), yields a W-boson mass that differs from its true value. Moreover, the best fit mass depends on the nature of the collider and the center-of-mass energy of collisions. We construct a barebones model that demonstrates this possibility quantitatively while satisfying current constraints. Interestingly, we find that the nature of the new physics particle and its interactions appear as a variation of the physics of Axion-like particles after a field redefinition.

Ankita Budhraja

Samadrita Mukherjee

Tuhin Roy

A twisted tale of the transverse-mass tail

A light axionlike particle or an axionlike particle (ALP) not just gives rise to interesting and spectacular signals of new physics as final states in meson decays, it necessarily leaves tell-tale signatures in processes that involve standard model (SM) fields only (i.e., SM processes). These effects result in the violation of the Gell-Mann-Okubo mass relation, modified form factors, altered integrated and differential rates for various SM transitions etc. This suggests that in the presence of a low lying state, such as an ALP, extraction of masses, mixing angles, and form factors in an entirely data-driven way from meson-physics observables is a highly nontrivial exercise. However, once done correctly, these same observables may, in turn, provide important (indirect) bounds on ALP physics, which remain robust even in the limits where new physics effects conspire to weaken the bounds from direct searches. Starting with a generalized ALP-quark Lagrangian (where restrictions due to parity are removed) we demonstrate this approach by focusing on <math><msubsup><mi>K</mi><msub><mo>ℓ</mo><mn>3</mn></msub><mo>+</mo></msubsup></math> decays, where we derive (indirect) bounds on ALP physics using <math><mrow><mi>NA</mi><mn>48</mn><mo>/</mo><mn>2</mn></mrow></math> data and lattice results. We also find sum rules that not just show deviations in the presence of an ALP but also give hints towards the specific nature of the ALP physics itself.

United States

Subhajit Ghosh

Tuhin S. Roy

Flavor physics with generalized ALP-quark couplings

With a design luminosity of 50 ab −1 and detectors with tracking capabilities extending beyond 1 m, the Belle II experiment is the perfect laboratory for the search of particles that couple weakly to the Standard Model and have a characteristic decay length of a few centimetres and more. We show that for models of dark photons and other light vector bosons, Belle II will be successful in probing regions of parameter space which are as of now unexplored by any experiment. In addition, for models where the vector boson couples sub-dominantly to the electron and quarks as compared to muons, e.g. in the L  μ  −L  τ  model, Belle II will probe regions of mass and couplings compatible with the anomalous magnetic moment of muon. We discuss these results and derive the projected sensitivity of Belle II for a handful of other models. Finally, even with the currently accumulated data, ∼ 200 fb −1, Belle II should be able to cover regions of parameter space pertaining to the X(17) boson postulated to solve the ATOMKI anomaly.

Italy

Sabyasachi Chakraborty

Sokratis Trifinopoulos

Displaced searches for light vector bosons at Belle II

Using the left-right symmetric model as an illustrative example, we suggest a simple and straightforward way of constraining the <math><msup><mi>W</mi><mo>′</mo></msup></math> mass directly from the decay of the Higgs boson to two photons. The proposed method is generic and applicable to a diverse range of models with a <math><msup><mi>W</mi><mo>′</mo></msup></math>-boson that couples to the Standard Model–like Higgs boson. Our analysis exemplifies how the precision measurement of the Higgs to diphoton signal strength can have a pivotal role in probing the scale of new physics.

Sweden

Dipankar Das

Roman Pasechnik

Johan Rathsman

Complementary bound on the <math><mrow><msup><mrow><mi>W</mi></mrow><mrow><mo>′</mo></mrow></msup></mrow></math> mass from Higgs boson to diphoton decays

In a truly model-independent approach, we reexamine a minimal extension of the Standard Model (SM) through the introduction of an additional <math><mrow><mi>U</mi><mo>(</mo><mn>1</mn><mo>)</mo></mrow></math> symmetry leading to a new neutral gauge boson (<math><mrow><msup><mrow><mi>Z</mi></mrow><mrow><mo>′</mo></mrow></msup></mrow></math>), allowing its kinetic mixing with the hypercharge gauge boson. An SM neutral scalar is used to spontaneously break this extra symmetry, leading to the mass of the <math><msup><mi>Z</mi><mo>′</mo></msup></math>. Except for three right-handed neutrinos, no other fermions are added. We use the current LHC Drell-Yan data to put model-independent constraints in the parameter space of three quantities, namely, <math><msub><mi>M</mi><msup><mi>Z</mi><mo>′</mo></msup></msub></math>, the <math><mrow><mi>Z</mi><mtext>−</mtext><msup><mrow><mi>Z</mi></mrow><mrow><mo>′</mo></mrow></msup></mrow></math> mixing angle (<math><msub><mi>α</mi><mi>z</mi></msub></math>), and the extra <math><mi>U</mi><mo>(</mo><mn>1</mn><mo>)</mo></math> effective gauge coupling (<math><msubsup><mi>g</mi><mi>x</mi><mo>′</mo></msubsup></math>), which absorb all model dependence. We impose additional constraints from unitarity and low-energy neutrino-electron scattering. However, limits extracted from direct searches turn out to be most stringent. We obtain <math><msub><mi>M</mi><msup><mi>Z</mi><mo>′</mo></msup></msub><mo>&gt;</mo><mn>4.4</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math> and <math><mo>|</mo><msub><mi>α</mi><mi>z</mi></msub><mo>|</mo><mo>&lt;</mo><mn>0.001</mn></math> at 95% C.L., when the strength of the additional <math><mi>U</mi><mo>(</mo><mn>1</mn><mo>)</mo></math> gauge coupling is the same as that of the SM <math><mi>S</mi><mi>U</mi><mo>(</mo><mn>2</mn><msub><mo>)</mo><mi>L</mi></msub></math>.

Gautam Bhattacharyya

Amitava Raychaudhuri

Reappraisal of constraints on <math><mrow><msup><mrow><mi>Z</mi></mrow><mrow><mo>′</mo></mrow></msup></mrow></math> models from unitarity and direct searches at the LHC

The ingredients for a model with a TeV right-handed scale, gauge coupling unification, and suitable dark matter candidates lie at the heart of left–right symmetry with broken D-parity. After detailing the contents of such a model, with <math><mi>S</mi><mi>U</mi><msub><mrow><mo>(</mo><mn>2</mn><mo>)</mo></mrow><mrow><mi>R</mi></mrow></msub></math> self-conjugate fermions at the right-handed scale aiding in unification of couplings, we explore its dark matter implications and collider signatures.

Left–right model with TeV fermionic dark matter and unification

The CMS experiment at the Large Hadron Collider has reported a 2.8Ï excess in the (2 e )(2 jets ) channel around 2.1 TeV. Interpretation of this data is reconsidered in terms of the production of a right-handed weak gauge boson, W R , of the left-right symmetric model and in an SO(10) grand unified theory abiding by the Extended Survival Hypothesis. The left-right symmetric model can be consistent with this excess if (a) the heavy right-handed neutrino has a mass near W R , or (b) if g L â g R , or (c) the right-handed CKM matrix is nontrivial. Combinations of the above possibilities are also viable. A W R with a mass in the TeV region if embedded in SO(10) is not compatible with g L = g R . Rather, it implies 0 . 64 â¤ g R /g L â¤ 0 . 78. Further, a unique symmetry-breaking route â the order being left-right discrete symmetry breaking first, followed by SU(4) C and finally SU(2) R â to the standard model is picked out. The L â R discrete symmetry has to be broken at around 10 16 GeV. The grand unification scale is pushed to 10 18 GeV making the detection of proton decay in ongoing searches rather unlikely. The SU(4) C breaking scale can be at its allowed lower limit of 10 6 GeV so that n â n Â¯ $$ n-\overline{n} $$ oscillation or flavour changing processes such as K L â Î¼e and B d,s â Î¼e may be detectable. The Higgs scalar multiplets responsible for SO(10) symmetry breaking at various stages are uniquely identified so long as one adheres to a minimalist principle. We also remark, en passant , about a partially unified Pati-Salam model.