New articles on High Energy Physics - Experiment

[1] 2404.12517

First results from the Axion Dark-Matter Birefringent Cavity (ADBC) experiment

Axions and axion-like particles are strongly motivated dark matter candidates that are the subject of many current ground based dark matter searches. We present first results from the Axion Dark-Matter Birefringent Cavity (ADBC) experiment, which is an optical bow-tie cavity probing the axion-induced birefringence of electromagnetic waves. Our experiment is the first optical axion detector that is tunable and quantum noise limited, making it sensitive to a wide range of axion masses. We have iteratively probed the axion mass range 40.9-43.3$\text{ neV/c}^2$, 49.3-50.6$\text{ neV/c}^2$, and 54.4-56.7$\text{ neV/c}^2$, and found no dark matter signal. On average, we constrain the ALP-photon coupling at the level $g_{a\gamma\gamma} \leq 1.9\times 10^{-8} \text{ GeV}^{-1}$. We also present prospects for future axion dark matter detection experiments using optical cavities.

[2] 2404.12660

Search for the non-resonant production of Higgs boson pairs via gluon fusion and vector-boson fusion in the $b\bar{b}τ^+τ^-$ final state in proton-proton collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector

A search for the non-resonant production of Higgs boson pairs in the $HH\rightarrow b\bar{b}\tau^+\tau^-$ channel is performed using 140 fb$^{-1}$ of proton-proton collisions at a centre-of-mass energy of $13$ TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. The analysis strategy is optimised to probe anomalous values of the Higgs boson self-coupling modifier $\kappa_\lambda$ and of the quartic $HHVV$ ($V = W,Z$) coupling modifier $\kappa_{2V}$. No significant excess above the expected background from Standard Model processes is observed. An observed (expected) upper limit $\mu_{HH}<5.9$ $(3.3)$ is set at 95% confidence-level on the Higgs boson pair production cross-section normalised to its Standard Model prediction. The coupling modifiers are constrained to an observed (expected) 95% confidence interval of $-3.1 < \kappa_\lambda < 9.0$ ($-2.5 < \kappa_\lambda < 9.3$) and $-0.5 < \kappa_{2V} < 2.7$ ($-0.2 < \kappa_{2V} < 2.4$), assuming all other Higgs boson couplings are fixed to the Standard Model prediction. The results are also interpreted in the context of effective field theories via constraints on anomalous Higgs boson couplings and Higgs boson pair production cross-sections assuming different kinematic benchmark scenarios.

[3] 2404.12731

Near-Quantum-limited Haloscope Detection of Dark Photon Dark Matter Enhanced by a High-Q Superconducting Cavit

We report new experimental results on the search for dark photons based on a near-quantum-limited haloscope equipped with a superconducting cavity. The loaded quality factor of the superconducting cavity is $6\times10^{5}$, so that the expected signal from dark photon dark matter can be enhanced by more than one order compared to a copper cavity. A Josephson parametric amplifier with a near-quantum-limited noise temperature has been utilized to minimize the noise during the search. Furthermore, a digital acquisition card based on field programmable gate arrays has been utilized to maximize data collection efficiency with a duty cycle being 100$\%$. This work has established the most stringent constraints on dark photons at around 26.965 $\mu$eV. In the future, our apparatus can be extended to search for other dark matter candidates, such as axions and axion-like particles, and scrutinize new physics beyond the Standard Model.

[4] 2404.12817

Determination of the CKM angle $φ_{3}$ from a combination of Belle and Belle II results

We report a determination of the CKM angle $\phi_{3}$, also known as $\gamma$, from a combination of measurements using samples of up to 711~fb$^{-1}$ from the Belle experiment and up to 362~fb$^{-1}$ from the Belle II experiment. We combine results from analyses of $B^+\to DK^+, B^+\to D\pi^+$, and $B^+ \to D^{*}K^+$ decays, where $D$ is an admixture of $D^0$ and $\overline{D}{}^{0}$ mesons, in a likelihood fit to obtain $\phi_{3} = (78.6^{+7.2}_{-7.3})^{\circ}$. We also briefly discuss the interpretation of this result.

[5] 2404.12915

Search for a resonance decaying into a scalar particle and a Higgs boson in the final state with two bottom quarks and two photons in proton-proton collisions at a center of mass energy of 13 TeV with the ATLAS detector

A search for the resonant production of a heavy scalar $X$ decaying into a Higgs boson and a new lighter scalar $S$, through the process $X \to S(\to bb) H(\to \gamma\gamma)$, where the two photons are consistent with the Higgs boson decay, is performed. The search is conducted using an integrated luminosity of 140 fb$^{-1}$ of proton-proton collision data at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider. The search is performed over the mass range 170 $\leq$ $m_{X}$ $\leq$ 1000 GeV and 15 $\leq$ $m_{S}$ $\leq$ 500 GeV. Parameterised neural networks are used to enhance the signal purity and to achieve continuous sensitivity in a domain of the ($m_{X}$, $m_{S}$) plane. No significant excess above the expected background is found and 95% CL upper limits are set on the cross section times branching ratio, ranging from 39 fb to 0.09 fb. The largest deviation from the background-only expectation occurs for ($m_{X}$, $m_{S}$) = (575, 200) GeV with a local (global) significance of 3.5 (2.0) standard deviations.

[6] 2404.06539

First Search for High-Energy Neutrino Emission from Galaxy Mergers

The exact sources of high-energy neutrinos detected by the IceCube neutrino observatory still remain a mystery. For the first time, this work explores the hypothesis that galaxy mergers may serve as sources for these high-energy neutrinos. Galaxy mergers can host very high-energy hadronic and photohadronic processes, which may produce very high-energy neutrinos. We perform an unbinned maximum-likelihood-ratio analysis utilizing the galaxy merger data from six catalogs and 10 years of public IceCube muon-track data to quantify any correlation between these mergers and neutrino events. First, we perform the single source search analysis, which reveals that none of the considered galaxy mergers exhibit a statistically significant correlation with high-energy neutrino events detected by IceCube. Furthermore, we conduct a stacking analysis with three different weighting schemes to understand if these galaxy mergers can contribute significantly to the diffuse flux of high-energy astrophysical neutrinos detected by IceCube. We find that upper limits (at $95\%$ c.l.) of the all flavour high-energy neutrino flux, associated with galaxy mergers considered in this study, at $100$ TeV with spectral index $\Gamma=-2$ are $2.57\times 10^{-18}$, $8.51 \times 10^{-19}$ and $2.36 \times 10^{-18}$ $\rm GeV^{-1}\,cm^2\,s^{-1}\,sr^{-1}$ for the three weighting schemes. This work shows that these selected galaxy mergers do not contribute significantly to the IceCube detected high energy neutrino flux. We hope that in the near future with more data, the search for neutrinos from galaxy mergers can either discover their neutrino production or impose more stringent constraints on the production mechanism of high-energy neutrinos within galaxy mergers.

[7] 2404.12425

Triple Higgs boson production and electroweak phase transition in the two-real-singlet model

The production of three Higgs bosons at hadron colliders can be enhanced by a double-resonant effect in the $\mathbb{Z}_2$-symmetric two-real-singlet extension of the Standard Model, making it potentially observable in future LHC runs. The production rate is maximized for large scalar couplings, which prompts us to carefully reconsider the perturbativity constraints on the theory. This leads us to construct a new set of 140 benchmark points that have a triple Higgs boson production cross-section at least 100 times larger than the SM value. Furthermore, we study the dynamics of the electroweak phase transition, both analytically at leading order, and numerically without the high-temperature expansion. Both analyses indicate that a first-order phase transition is incompatible with the requirement that both singlets have a non-zero vev in the present-day vacuum, as required by doubly-enhanced triple Higgs boson production. Allowing instead one of the singlets to remain at zero field value opens up the possibility of a first-order phase transition, while di-Higgs boson production can still be enhanced by a (single) resonance.

[8] 2404.12442

Minimal complete tri-hypercharge theories of flavour

The tri-hypercharge proposal introduces a separate gauged weak hypercharge assigned to each fermion family as the origin of flavour. This is arguably one of the simplest setups for building "gauge non-universal theories of flavour" or "flavour deconstructed theories". In this paper we propose and study two minimal but ultraviolet complete and renormalisable tri-hypercharge models. We show that both models, which differ only by the heavy messengers that complete the effective theory, are able to explain the observed patterns of fermion masses and mixings (including neutrinos) with all fundamental coefficients being of $\mathcal{O}(1)$. In fact, both models translate the complicated flavour structure of the Standard Model into three simple physical scales above electroweak symmetry breaking, completely correlated with each other, that carry meaningful phenomenology. In particular, the heavy messenger sector determines the origin and size of fermion mixing, which controls the size and nature of the flavour-violating currents mediated by the two heavy $Z'$ gauge bosons of the theory. The phenomenological implications of the two minimal models are compared. In both models the lightest $Z'$ remains discoverable in dilepton searches at the LHC Run 3.

[9] 2404.12497

Novel indium phosphide charged particle detector characterization with a 120 GeV proton beam

Thin film detectors which incorporate semiconductor materials other than silicon have the potential to build upon their unique material properties and offer advantages such as faster response times, operation at room temperature, and radiation hardness. To explore the possibility, promising candidate materials were selected, and particle tracking detectors were fabricated. An indium phosphide detector with a metal-insulator-metal (MIM) structure has been fabricated for particle tracking. The detector was tested using radioactive sources and a high energy proton beam at Fermi National Accelerator Laboratory. In addition to its simplistic design and fabrication process, the indium phosphide particle detector showed a very fast response time of hundreds of picoseconds for the 120 GeV protons, which are comparable to the ultra-fast silicon detectors. This fast-timing response is attributed to the high electron mobility of indium phosphide. Such material properties can be leveraged to build novel detectors with superlative performance.

[10] 2404.12654

Semileptonic $Ω_{b}\rightarrow Ω_{c}{\ell}\barν_{\ell}$ transition in full QCD

We investigate the semileptonic decay of $\Omega_b\to\Omega_c~{\ell}\bar\nu_{\ell}$ in three lepton channels. To this end, we use QCD sum rule method in three point framework to calculate the form factors defining the matrix elements of these transitions. Having calculated the form factors as building blocks, we calculate the decay widths and branching fractions of the exclusive decays in all lepton channels and compare the results with other theoretical predictions. The obtained results for branching ratios and ratio of branching fractions at different leptonic channels may help experimental groups in their search for these weak decays. Comparison of the obtained results with possible future experimental data can be useful to check the order of consistency between the standard model theory predictions and data on the heavy baryon decays.

[11] 2404.12781

Search for Z' Radiating from the Dark Matter at the LHC

We discuss a collider probe of a dark sector model in which the dark matter is charged under a new, hidden $U(1)$ gauge group. In particular, we look for the so-called Darkstrahlung process, in which the final states dark matter radiates a new $Z'$ gauge boson and it manifests as dilepton resonances. This work emphasizes the potential of dilepton final states with missing transverse energy in probing the darkstrahlung process. We recast the ATLAS Run 2 search for dilepton resonances in association with missing energy in addition to the ATLAS and CMS searches for sleptons. We find that the recasted searches put strong constraints on the coupling between the dark matter and the $Z'$. Moreover, we evaluate refined search strategies for $Z'$ production and propose an analysis employing constraints on the lepton invariant mass and higher missing energy cut related to the darkstrahlung process. Simulation outcomes indicate substantial enhancements, particularly by a factor of 6 in regions featuring lower $Z'$ masses. Finally, we also discuss the case when the $Z'$ has a long lifetime, resulting in displaced decay of the boson.

[12] 2404.12809

Mapping the SMEFT at High-Energy Colliders: from LEP and the (HL-)LHC to the FCC-ee

We present SMEFiT3.0, an updated global SMEFT analysis of Higgs, top quark, and diboson production data from the LHC complemented by electroweak precision observables (EWPOs) from LEP and SLD. We consider recent inclusive and differential measurements from the LHC Run II, alongside with a novel implementation of the EWPOs based on independent calculations of the relevant EFT contributions. We estimate the impact of HL-LHC measurements on the SMEFT parameter space when added on top of SMEFiT3.0, through dedicated projections extrapolating from Run II data. We quantify the significant constraints that measurements from two proposed high-energy circular $e^+e^-$ colliders, the FCC-ee and the CEPC, would impose on both the SMEFT parameter space and on representative UV-complete models. Our analysis considers projections for the FCC-ee and the CEPC based on the latest running scenarios and includes $Z$-pole EWPOs, fermion-pair, Higgs, diboson, and top quark production, using optimal observables for both the $W^+W^-$ and the $t\bar{t}$ channels. The framework presented in this work may be extended to other future colliders and running scenarios, providing timely input to ongoing studies towards future high-energy particle physics facilities.