arXiv subjects

Suchita Kulkarni

Publications and source records attributed to Suchita Kulkarni.

At least 19 recordsLinked to original sources

arXiv2026

Semi-visible emerging jets

We propose a new class of dark-shower signatures in Standard Model extensions featuring Hidden Valleys or dark sectors coupled through an s-channel mediator. In this framework, unstable dark pions appear as long-lived particles (LLPs), with their lifetimes treated as free parameters. The resulting signatures, which we term semi-visible emerging jets (SVEJ), continuously interpolate between the established semi-visible and emerging jet regimes. We outline an analysis strategy optimized for dark pion lifetimes of order $\mathcal{O}(10)$ mm, and reinterpret existing LLP searches targeting lifetimes of $\mathcal{O}(100)$-$\mathcal{O}(1000)$ mm. Our proposed SVEJ search, exploiting the current ATLAS emerging-jet trigger, achieves sensitivity to cross sections of $\mathcal{O}(0.1)$ fb for lifetimes around $\mathcal{O}(10)$ mm. Finally, we advocate a more detailed study, including hadronization uncertainties and detector-level effects.

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arXiv2026

Probing $ν$SMEFT at Belle II with displaced dilepton vertices

The existence of right-handed (RH) neutrinos is strongly motivated by the observation of small neutrino masses and as a means to shed light on the origin of parity violation in the Standard Model (SM). Experimental searches for the corresponding mass eigenstates, referred to as heavy neutral leptons (HNLs), have been carried out in a variety of experiments and within different HNL models. In the current work we use the SM effective field theory with added RH neutrinos, known as $ν$SMEFT, to study GeV-scale HNL production in $e^+e^-$ collisions at the Belle~II experiment. We focus on leptonic decays of long-lived HNLs that produce a displaced vertex in the Belle~II detector. Accounting for detection efficiency and backgrounds, we estimate the sensitivity of Belle~II to the new-physics scale of four-fermion, Higgs-current, and dipole operators in $ν$SMEFT. We find that for most operators, the search we propose probes large regions of parameter space that are not excluded by other searches.

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arXiv2026

Sub-GeV dark matter and multi-decay signatures from dark showers at beam-dump experiments

In models of strongly-interacting dark sectors, the production of dark quarks at accelerators can give rise to dark showers with multiple dark mesons in the final state. If some of these dark mesons are sufficiently light and long-lived, they can be detected with searches for displaced vertices at beam-dump experiments and electron-positron colliders. In this work we focus on the case that dark quark production proceeds via effective operators, while the dark sector analogue of the $ρ^0$ meson can decay via kinetic mixing. We evaluate current constraints from NA62 and BaBar as well as sensitivity projections for SHiP and Belle II. We find that there exists a sizable parameter region where SHiP may detect several displaced vertices in a single event and thus obtain valuable information about the structure of the dark sector.

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arXiv2026

NLO observables for QCD-like theories and application to pion dark matter

QCD-like theories are of interest in various areas of beyond-Standard-Model phenomenology, including composite Higgs models or pionic dark matter. The effective field theories provide a framework for describing the dynamics of such strongly coupled gauge theories at low energies. In this work, we present next-to-leading order (NLO) expressions for masses, condensates, decay constants, and scattering amplitudes in the chiral expansion of QCD-like theories with $N_F=2$ fermions with non-degenerate masses in both real and pseudoreal representations of the gauge group. We further apply the NLO formulas to fit existing lattice spectroscopic and scattering data for $Sp(N_c=4)$ gauge theory with $N_F=2$ fermions in fundamental representation, extracting the NLO low-energy constants of the theory. Using these fits, we refine the NLO formulas describing the $2\to 2$ pion self-interactions and confirm that the NLO contributions play a crucial role in determining the viable parameter space of pion dark matter scenarios like the strongly interacting massive particles (SIMP).

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arXiv2026

Sterile Neutrinos at MAPP in the B-L Model

The possibility of searching for right-handed neutrinos at the MoEDAL's Apparatus for Penetrating Particles (MAPP) detector is investigated in this work. In particular, pair-production of right-handed (RH) neutrinos $N$ from either a $B-L$ gauge boson $Z'$, as well as Standard Model (SM) $Z$ boson are considered. Under a no-background assumption, we show that the MAPP detector can be sensitive to active-sterile neutrino mixing strengths as low as $V_{μN}^2 \approx 10^{-12}$ for multiple choices of $m_N / m_{Z'}$ values, when taking the $B-L$ gauge coupling $g_{B-L} = 10^{-3}$ near its current limit. The SM $Z$ boson portal can reach a similar sensitivity, when the effective mixing between the $B-L$ and SM gauge boson is $α\approx 0.002$.

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arXiv2026

Strongly Interacting Dark Matter admixed Neutron Stars

Dark matter may accumulate in neutron stars given its gravitational interaction and abundance. We investigate the influence of strongly-interacting dark matter, described by a QCD-like one-flavor $G_2$ gauge theory, on neutron stars. This choice allows to test, for the first time, a first-principles-determined non-Abelian dark matter equation of state, which supports composite fermionic dark matter and thus a Fermi-pressure-stabilized dark matter component. The ordinary matter part of the mixed star is described by available model-agnostic equations of state that interpolate between the low-density regime and high-density regime. We find that strongly-interacting dark matter has a similar impact on neutron stars as other model equation of states and confirm that strongly-interacting dark matter can be accommodated by constraints from neutron star observations within our uncertainties.

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arXiv2025

Constraining the SMEFT Extended with Sterile Neutrinos at FCC-ee

We investigate how extensions of the Standard Model (SM) involving heavy neutral leptons (HNLs) can be probed at FCC-ee, the proposed high-energy circular $e^+e^-$ collider. Using the effective field theory (EFT) approach, we determine the impact of new interactions on the production and decay of HNLs at FCC-ee. In particular, we consider $d\leq 7$ $ν$SMEFT operators which induce vector, scalar and tensor four-fermion and effective charged- and neutral-current interactions of HNLs, that may also mix with the active neutrinos of the SM. We consider sensitivities to the active-sterile mixing and EFT Wilson coefficients from monophoton searches and displaced vertex decay signatures. In both analyses, we consider the scenarios where HNLs are Majorana or Dirac fermions. We translate the upper bounds on the Wilson coefficients to lower limits on the scale of new physics.

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arXiv2025

Hidden valley scenario sensitivity in the CMS muon endcap detector

We study the sensitivity of the CMS search to displaced showers arising from the decays of long-lived particles in the muon system, within the framework of Hidden Valley scenarios. To establish our simulation setup, we employ a parameterization of Hidden Valley theory space and adopt a hybrid strategy where the lifetime is treated as a free parameter to provide model-independent Hidden Valley quark production cross-section upper limits. Our results indicate that the CMS search is broadly sensitive to variations in Hidden Valley parameters such as the overall scale and relevant mass ratios, while showing comparatively weak dependence on the number of Hidden Valley colors or flavors. The exact quantitative results we derive depend on the underlying hadronization model employed and thus, we urge caution in interpreting the results. Within these limitations, we also establish model-dependent limits on the maximum strength of the mediator coupling to Hidden Valley quarks. Our approach illustrates how one can move beyond simplified model strategies by employing a first-principles-inspired theory setup, while highlighting the theoretical uncertainties inherent in modeling Hidden Valley phenomenology.

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arXiv2025

Surveying the theory space of pion dark matter

We use a holographic model to survey the space of strongly coupled SU(Nc) gauge dynamics with QCD-like chiral symmetry breaking pattern for quarks in the fundamental representation. We systematically identify the light degrees of freedom (rho, sigma and pi mesons) that would make up the dark sector as a function of Nf, Nc and a common quark mass scale. We identify seven distinct effective theories that are of interest to explore and make a first summary of the expected dark matter phenomenology. Amongst our results we conclude that QCD-like models where the low energy theory is described purely in terms of pions struggle to generate a large enough Mpi/fpi value so these theories will need extra relic density generation mechanisms to be viable. The largest space of models (with an intermediate quark mass) have both the sigma and rho lying below 2 Mpi and are largely unexplored in the literature so far. Regions with just one of rho or sigma light are possible in constrained parameter regions. These states aid the pion relic density generation as needed for valid theories. The sigma always lies above the pi mass becoming degenerate with the pi in the extreme walking limit.

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arXiv2025

On the Simulation of Hidden Parton Showers in the Conformal Window

We consider confining Hidden Valley/Dark Sector theories containing many dark quark flavors. These theories are in the ``conformal window'': they reach an infrared fixed point when their quarks are massless, and have unfamiliar confinement when the quark masses are non-zero but small. Their jets of hidden hadrons may be quite different from those familiar from QCD, but their details cannot currently be simulated even qualitatively. This is partly due to the use of approximations to the two-loop running coupling in existing event generators' parton showers, which are not broadly applicable across the conformal window. We argue that the exact two-loop running coupling, and a corresponding Sudakov factor employing that coupling, must be implemented in simulation packages in order to allow phenomenological studies of these theories.

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arXiv2025

Revealing the Origin of Neutrino Masses through Displaced Shower Searches in the CMS Muon System

We study the potential to probe the origin of neutrino masses, by searching for long-lived right-handed neutrinos (RHNs) $N$ in the $B-L$ model and in the RHN-extended Standard Model (SM) Effective Field Theory (EFT). Despite the small active-sterile mixing $|V_{\ell N}|^2$, RHNs are produced abundantly via SM and exotic Higgs production, as long as the Higgs mixing or EFT operator coefficient is sufficiently large. We reinterpret a search for displaced showers in the CMS muon system and we find that it is sensitive to parameter space at and below the seesaw floor, $|V_{\ell N}|^2 \approx 10^{-12}$ ($\ell = e$, $τ$) for $m_N \approx 40$ GeV. With existing data constraining such well-motivated scenarios of neutrino mass generation, we determine the projected sensitivity at the HL-LHC, motivating dedicated searches for long-lived RHNs with decay lengths $\approx 10$ m.

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arXiv2024

Dark Sector Showers and Hadronisation in Herwig 7

We present a novel simulation of a strongly interacting dark sector also known as the Hidden Valley scenarios using angular ordered showers and the cluster hadronisation model in Herwig 7. We discuss the basics of this implementation and the scale hierarchies underpinning the simulation. With the help of a few benchmarks, we show the effect of variation of dark sector parameters on thrust and angularities within the dark sector, and study correlation functions, which can be helpful for understanding the angular structure of these events. Finally we comment on the uncertainties introduced due to lack of knowledge of hadronisation parameters within the dark sectors.

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arXiv2024

Dark matter relic density in strongly interacting dark sectors with light vector mesons

Stable dark matter particles may arise as pseudo-Goldstone bosons from the confinement of dark quarks interacting via a non-Abelian gauge force. Their relic abundance is determined not by annihilations into visible particles but by dark pion number-changing processes within the dark sector, such as $3 π_D \to 2 π_D$. However, if the dark vector mesons $ρ_D$ are light enough for $3 π_D \to π_D ρ_D$ annihilations to be kinematically allowed, this process dominates and significantly delays freeze-out. As a result, the preferred dark matter mass scale increases and bounds from the Bullet Cluster can be evaded.

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arXiv2024

Low energy effective theories of composite dark matter with real representations

We consider pseudo Nambu-Goldstone bosons arising from Dirac fermions transforming in real representations of a confining gauge group as dark matter candidates. We consider a special case of two Dirac fermions and couple the resulting dark sector to the Standard Model using a vector mediator. Within this construction, we develop a consistent low energy effective theory, with special attention to Wess-Zumino-Witten term given the topologically non-trivial coset space. We furthermore include the heavier spin-0 flavour singlet state and the spin-1 vector meson multiplet, by using the Hidden Local Symmetry Lagrangian for the latter. Although we concentrate on special case of two flavours, our results are generic and can be applied to a wider variety of theories featuring real representations. We apply our formalism and comment on the effect of the flavour singlet for dark matter phenomenology. Finally, we also comment on generalisation of our formalism for higher representations and provide potential consequences of discrete symmetry breaking.

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arXiv2024

Dark Matter and Exotic Neutrino Interactions in Direct Detection Searches

We investigate the effect of new physics interacting with both Dark Matter (DM) and neutrinos at DM direct detection experiments. Working within a simplified model formalism, we consider vector and scalar mediators to determine the scattering of DM as well as the modified scattering of solar neutrinos off nuclei. Using existing data from LUX as well as the expected sensitivity of LUX-ZEPLIN and DARWIN, we set limits on the couplings of the mediators to quarks, neutrinos and DM. Given the current limits, we also assess the true DM discovery potential of direct detection experiments under the presence of exotic neutrino interactions. In the case of a vector mediator, we show that the DM discovery reach of future experiments is affected for DM masses $m_χ\lesssim 10$ GeV or DM scattering cross sections $σ_χ\lesssim 10^{-47}$ cm$^2$. On the other hand, a scalar mediator will not affect the discovery reach appreciably.

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arXiv2023

MITP Colours in Darkness workshop summary report

This report summarises the talks and discussions that took place over the course of the MITP Youngst@rs Colours in Darkness workshop 2023. All talks can be found at https://indico.mitp.uni-mainz.de/event/377/.

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arXiv2023

Heavy Neutrinos at the FCC-hh in the $U(1)_{B-L}$ Model

We investigate the potential of the 100 TeV future circular collider (FCC-hh) to probe heavy neutrinos. We concentrate in particular on heavy neutrino production via a $U(1)_{B-L}$ $Z'$ gauge boson and contrast the resulting limits with that mediated by Standard Model weak currents. We consider heavy neutrino decays to semi-leptonic as well as fully leptonic final states, particularly with muon flavour, and we show the importance of considering searches both in prompt and displaced decays of the heavy neutrinos. For prompt final states, semi-leptonic modes are more promising due to smaller background and larger yields, and TeV-scale heavy neutrinos with active-sterile mixing compatible with light neutrino mass generation in a seesaw scenario can be probed for a 5 TeV $Z'$ and gauge coupling as low as $g_{B-L} = 10^{-2}$. Displaced vertex searches can extend this range to heavy neutrino masses as low as 10 GeV.

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arXiv2022

Strongly Interacting Dark Matter from $Sp(4)$ Gauge Theory

The stable hadronic bound states in a hidden new non-Abelian gauge sector provide interesting candidates for strongly-interacting Dark Matter (DM). A particular example are theories in which DM is made up of dark pions which set the DM relic abundance through self-annihilation. One of the simplest realizations is $Sp(4)_c$ gauge theory with two Dirac fermions. We discuss its mesonic multiplets for degenerate and non-degenerate fermions, construct a low-energy effective theory and present lattice results for the pseudoscalar mesons and vector mesons.

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