Pich, A., & Rodriguez-Sanchez, A. (2022). Violations of quark-hadron duality in low-energy determinations of alpha(s). J. High Energy Phys., 07(7), 145–42pp.
Abstract: Using the spectral functions measured in tau decays, we investigate the actual numerical impact of duality violations on the extraction of the strong coupling. These effects are tiny in the standard alpha(s)(m(tau)(2)) determinations from integrated distributions of the hadronic spectrum with pinched weights, or from the total tau hadronic width. The pinched-weight factors suppress very efficiently the violations of duality, making their numerical effects negligible in comparison with the larger perturbative uncertainties. However, combined fits of alpha(s) and duality-violation parameters, performed with non-protected weights, are subject to large systematic errors associated with the assumed modelling of duality-violation effects. These uncertainties have not been taken into account in the published analyses, based on specific models of quark-hadron duality.
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Botella, F. J., Cornet-Gomez, F., Miro, C., & Nebot, M. (2022). Muon and electron g-2 anomalies in a flavor conserving 2HDM with an oblique view on the CDF M-W value. Eur. Phys. J. C, 82(10), 915–25pp.
Abstract: We consider a type I or type X two Higgs doublets model with a modified lepton sector. The generalized lepton sector is also flavor conserving but with the new Yukawa couplings completely decoupled from lepton mass proportionality. The model is one loop stable under renormalization group evolution and it allows to reproduce the g – 2 muon anomaly together with the different scenarios one can consider for the electron g – 2 anomaly, related to the Cesium and/or to the Rubidium recoilmeasurements of the fine structure constant. Thorough parameter space analyses are performed to constrain all the model parameters in the different scenarios, either including or not including the recent CDF measurement of the W boson mass. For light new scalars with masses in the 0.2-1.0 TeV range, the muon anomaly receives dominant one loop contributions; it is for heavy new scalars with masses above 1.2 TeV that two loop Barr-Zee diagrams are needed. The electron g-2 anomaly, if any, must always be obtained with the two loop contributions. The final allowed regions are quite sensitive to the assumptions about perturbativity of Yukawa couplings, which influence unexpected observables like the allowed scalar mass ranges. On that respect, intermediate scalar masses, highly constrained by direct LHC searches, are allowed provided that the new lepton Yukawa couplings are fully scrutinized, including values up to 250 GeV. In the framework of a complete model, fully numerically analysed, we show the implications of the recent M-W measurement.
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Capozzi, F., Chakraborty, M., Chakraborty, S., & Sen, M. (2022). Supernova fast flavor conversions in 1+1D: Influence of mu-tau neutrinos. Phys. Rev. D, 106(8), 083011–9pp.
Abstract: In the dense supernova environment, neutrinos can undergo fast flavor conversions which depend on the large neutrino-neutrino interaction strength. It has been recently shown that both their presence and outcome can be affected when passing from the commonly used three neutrino species approach to the more general one with six species. Here, we build up on a previous work performed on this topic and perform a numerical simulation of flavor evolution in both space and time, assuming six neutrino species. We find that the results presented in our previous work remain qualitatively the same even for flavor evolution in space and time. This emphasizes the need for going beyond the simplistic approximation with three species when studying fast flavor conversions.
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ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cardillo, F., et al. (2023). Search for heavy, long-lived, charged particles with large ionisation energy loss in pp collisions at root s=13 TeV using the ATLAS experiment and the full Run 2 dataset. J. High Energy Phys., 06(6), 158–60pp.
Abstract: This paper presents a search for hypothetical massive, charged, long-lived particles with the ATLAS detector at the LHC using an integrated luminosity of 139 fb(-1) of proton-proton collisions at root s = 13 TeV. These particles are expected to move significantly slower than the speed of light and should be identifiable by their high transverse momenta and anomalously large specific ionisation losses, dE/dx. Trajectories reconstructed solely by the inner tracking system and a dE/dx measurement in the pixel detector layers provide sensitivity to particles with lifetimes down to O(1) ns with a mass, measured using the Bethe-Bloch relation, ranging from 100 GeV to 3 TeV. Interpretations for pair-production of R-hadrons, charginos and staus in scenarios of supersymmetry compatible with these particles being long-lived are presented, with mass limits extending considerably beyond those from previous searches in broad ranges of lifetime.
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Arganda, E., Marcano, X., Martin Lozano, V., Medina, A. D., Perez, A. D., Szewc, M., et al. (2022). A method for approximating optimal statistical significances with machine-learned likelihoods. Eur. Phys. J. C, 82(11), 993–14pp.
Abstract: Machine-learning techniques have become fundamental in high-energy physics and, for new physics searches, it is crucial to know their performance in terms of experimental sensitivity, understood as the statistical significance of the signal-plus-background hypothesis over the background-only one. We present here a simple method that combines the power of current machine-learning techniques to face high-dimensional data with the likelihood-based inference tests used in traditional analyses, which allows us to estimate the sensitivity for both discovery and exclusion limits through a single parameter of interest, the signal strength. Based on supervised learning techniques, it can perform well also with high-dimensional data, when traditional techniques cannot. We apply the method to a toy model first, so we can explore its potential, and then to a LHC study of new physics particles in dijet final states. Considering as the optimal statistical significance the one we would obtain if the true generative functions were known, we show that our method provides a better approximation than the usual naive counting experimental results.
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Song, J., Feijoo, A., & Oset, E. (2022). Role of meson interactions in the D-s(+) -> pi(+) pi(+) pi(-) eta decay. Phys. Rev. D, 106(7), 074027–20pp.
Abstract: We perform a theoretical study of the D-s(+) ->pi(+)pi(+)pi(-)eta decay. We look first at the basic D-s(+) decay at the quark level from external and internal emission. Then we hadronize a pair or two pairs of q (q) over bar states to have mesons at the end. Posteriorly the pairs of mesons are allowed to undergo final state interaction, by means of which the a(0)(980), f(0)(980), a(1)(1260), and b(1)(1235) resonances are dynamically generated. The G parity is used as a filter of the possible channels, and from those with negative G parity only the ones that can lead to pi(+)pi(+)pi(-)eta at the final state are kept. Using transition amplitudes from the chiral unitary approach that generates these resonances and a few free parameters, we obtain a fair reproduction of the six mass distributions reported in the BESIII experiment.
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LHCb Collaboration(Aaij, R. et al), Jaimes Elles, S. J., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Rebollo De Miguel, M., et al. (2023). Measurement of the Prompt D0 Nuclear Modification Factor in p-Pb Collisions at √SNN=8.16 TeV. Phys. Rev. Lett., 131(10), 102301–12pp.
Abstract: The production of prompt D0 mesons in proton-lead collisions in both the forward and backward rapidity regions at a center-of-mass energy per nucleon pair of √SNN= = 8.16 TeV is measured by the sNN LHCb experiment. The nuclear modification factor of prompt D0 mesons is determined as a function of the transverse momentum pT, and the rapidity in the nucleon-nucleon center-of-mass frame y*. In the forward rapidity region, significantly suppressed production with respect to pp collisions is measured, which provides significant constraints on models of nuclear parton distributions and hadron production down to the very low Bjorken-x region of similar to 10-5. In the backward rapidity region, a suppression with a significance of 2.0-3.8 standard deviations compared to parton distribution functions in a nuclear environment expectations is found in the kinematic region of pT 6 GeV/c and -3.25 < y* < -2.5, corresponding to x similar to 0.01.
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ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cantero, J., et al. (2023). Production of Upsilon(nS) mesons in Pb plus Pb and pp collisions at 5.02 TeV. Phys. Rev. C, 107(5), 054912–25pp.
Abstract: A measurement of the production of vector bottomonium states, Upsilon(1S), Upsilon(2S), and Upsilon(3S), in Pb + Pb and pp collisions at a center-of-mass energy per nucleon pair of 5.02 TeV is presented. The data correspond to integrated luminosities of 1.38 nb(-1) of Pb + Pb data collected in 2018, 0.44 nb-1 of Pb + Pb data collected in 2015, and 0.26 fb(-1) of pp data collected in 2017 by the ATLAS detector at the Large Hadron Collider. The measurements are performed in the dimuon decay channel for transverse momentum p(T)(mu mu) < 30 GeV, absolute rapidity vertical bar y(mu mu)vertical bar < 1.5, and Pb + Pb event centrality 0-80%. The production rates of the three bottomonium states in Pb + Pb collisions are compared with those in pp collisions to extract the nuclear modification factors as functions of event centrality, p(T)(mu mu), and vertical bar y(mu mu)vertical bar. In addition, the suppression of the excited states relative to the ground state is studied. The results are compared with theoretical model calculations.
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ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Cabrera Urban, S., Cantero, J., et al. (2023). Differential t(t)over-tilde cross-section measurements using boosted top quarks in the all-hadronic final state with 139 fb(-1) of ATLAS data. J. High Energy Phys., 04(4), 080–108pp.
Abstract: Measurements of single-, double-, and triple-differential cross-sections are presented for boosted top-quark pair-production in 13 TeV proton-proton collisions recorded by the ATLAS detector at the LHC. The top quarks are observed through their hadronic decay and reconstructed as large-radius jets with the leading jet having transverse momentum (p(T)) greater than 500 GeV. The observed data are unfolded to remove detector effects. The particle-level cross-section, multiplied by the t (t) over bar branching fraction and measured in a fiducial phase space defined by requiring the leading and second-leading jets to have p(T)> 500 GeV and p(T)> 350 GeV, respectively, is 331 +/- 3(stat.) +/- 39(syst.) fb. This is approximately 20% lower than the prediction of 398(-49)(+48) fb by Powheg+Pythia 8 with next-to-leading-order (NLO) accuracy but consistent within the theoretical uncertainties. Results are also presented at the parton level, where the effects of top-quark decay, parton showering, and hadronization are removed such that they can be compared with fixed-order next-to-next-to-leading-order (NNLO) calculations. The parton-level cross-section, measured in a fiducial phase space similar to that at particle level, is 1.94 +/- 0.02(stat.) +/- 0.25(syst.) pb. This agrees with the NNLO prediction of 1.96(-0.17)(+0.02) pb. Reasonable agreement with the differential cross-sections is found for most NLO models, while the NNLO calculations are generally in better agreement with the data. The differential cross-sections are interpreted using a Standard Model effective field-theory formalism and limits are set on Wilson coefficients of several four-fermion operators.
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Martinelli, M., Scarcella, F., Hogg, N. B., Kavanagh, B. J., Gaggero, D., & Fleury, P. (2022). Dancing in the dark: detecting a population of distant primordial black holes. J. Cosmol. Astropart. Phys., 08(8), 006–47pp.
Abstract: Primordial black holes (PBHs) are compact objects proposed to have formed in the early Universe from the collapse of small-scale over-densities. Their existence may be detected from the observation of gravitational waves (GWs) emitted by PBH mergers, if the signals can be distinguished from those produced by the merging of astrophysical black holes. In this work, we forecast the capability of the Einstein Telescope, a proposed third-generation GW observatory, to identify and measure the abundance of a subdominant population of distant PBHs, using the difference in the redshift evolution of the merger rate of the two populations as our discriminant. We carefully model the merger rates and generate realistic mock catalogues of the luminosity distances and errors that would be obtained from GW signals observed by the Einstein Telescope. We use two independent statistical methods to analyse the mock data, finding that, with our more powerful, likelihood-based method, PBH abundances as small as fPBH approximate to 7 x 10(-6) ( fPBH approximate to 2 x 10(-6)) would be distinguishable from f(PBH) = 0 at the level of 3 sigma with a one year (ten year) observing run of the Einstein Telescope. Our mock data generation code, darksirens, is fast, easily extendable and publicly available on GitLab.
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