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Black, K. M. et al, & Zurita, J. (2024). Muon Collider Forum report. J. Instrum., 19(2), T02015–95pp.
Abstract: A multi-TeV muon collider offers a spectacular opportunity in the direct exploration of the energy frontier. Offering a combination of unprecedented energy collisions in a comparatively clean leptonic environment, a high energy muon collider has the unique potential to provide both precision measurements and the highest energy reach in one machine that cannot be paralleled by any currently available technology. The topic generated a lot of excitement in Snowmass meetings and continues to attract a large number of supporters, including many from the early career community. In light of this very strong interest within the US particle physics community, Snowmass Energy, Theory and Accelerator Frontiers created a cross-frontier Muon Collider Forum in November of 2020. The Forum has been meeting on a monthly basis and organized several topical workshops dedicated to physics, accelerator technology, and detector R&D. Findings of the Forum are summarized in this report.
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Domcke, V., Garcia-Cely, C., Lee, S. M., & Rodd, N. L. (2024). Symmetries and selection rules: optimising axion haloscopes for Gravitational Wave searches. J. High Energy Phys., 03(3), 128–51pp.
Abstract: In the presence of electromagnetic fields, both axions and gravitational waves (GWs) induce oscillating magnetic fields: a potentially detectable fingerprint of their presence. We demonstrate that the response is largely dictated by the symmetries of the instruments used to search for it. Focussing on low mass axion haloscopes, we derive selection rules that determine the parametric sensitivity of different detector geometries to axions and GWs, and which further reveal how to optimise the experimental geometry to maximise both signals. The formalism allows us to forecast the optimal sensitivity to GWs in the range of 100 kHz to 100 MHz for instruments such as ABRACADABRA, BASE, ADMX SLIC, SHAFT, WISPLC, and DMRadio.
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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. (2024). Measurement of J/ψ-pair production in pp collisions at √s=13 TeV and study of gluon transverse-momentum dependent PDFs. J. High Energy Phys., 03(3), 088–40pp.
Abstract: The production cross-section of J/psi pairs in proton-proton collisions at a centre-of-mass energy of root s = 13TeV is measured using a data sample corresponding to an integrated luminosity of 4.2 fb(-1) collected by the LHCb experiment. The measurement is performed with both J/psi mesons in the transverse momentum range 0 < p(T) < 14 GeV/c and rapidity range 2.0 < y < 4.5. The cross-section of this process is measured to be 16.36 +/- 0.28 (stat) +/- 0.88 (syst) nb. The contributions from single-parton scattering and double-parton scattering are separated based on the dependence of the cross-section on the absolute rapidity difference Delta y between the two J/psi mesons. The effective cross-section of double-parton scattering is measured to be sigma(eff) = 13.1 +/- 1.8 (stat) +/- 2.3 (syst) mb. The distribution of the azimuthal angle phi(CS) of one of the J/psi mesons in the Collins-Soper frame and the p(T)-spectrum of the J/psi pairs are also measured for the study of the gluon transverse-momentum dependent distributions inside protons. The extracted values of < cos4 phi(CS)> and < cos2 phi(CS)> are consistent with zero, but the presence of azimuthal asymmetry at a few percent level is allowed.
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Shi, P. P., Baru, V., Guo, F. K., Hanhart, C., & Nefediev, A. (2024). Production of the X(4014) as the Spin-2 Partner of X(3872) in e + e – Collisions. Chin. Phys. Lett., 41(3), 031301–7pp.
Abstract: In 2021, the Belle collaboration reported the first observation of a new structure in the psi(2S)gamma final state produced in the two-photon fusion process. In the hadronic molecule picture, this new structure can be associated with the shallow isoscalar D*D* bound state and as such is an excellent candidate for the spin-2 partner of the X(3872) with the quantum numbers J(PC) = 2(++) conventionally named X-2. In this work we evaluate the electronic width of this new state and argue that its nature is sensitive to its total width, the experimental measurement currently available being unable to distinguish between different options. Our estimates demonstrate that the planned Super tau-Charm Facility offers a promising opportunity to search for and study this new state in the invariant mass distributions for the final states J/psi gamma and psi(2S)gamma.
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Aebischer, J. et al, & Vicente, A. (2024). Computing tools for effective field theories. Eur. Phys. J. C, 84(2), 170–59pp.
Abstract: In recent years, theoretical and phenomenological studies with effective field theories have become a trending and prolific line of research in the field of high-energy physics. In order to discuss present and future prospects concerning automated tools in this field, the SMEFT-Tools 2022 workshop was held at the University of Zurich from 14th-16th September 2022. The current document collects and summarizes the content of this workshop.
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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. (2024). Observation of Cabibbo-Suppressed Two-Body Hadronic Decays and Precision Mass Measurement of the Ω0c Baryon. Phys. Rev. Lett., 132(8), 081802–11pp.
Abstract: The first observation of the singly Cabibbo-suppressed 0c -> -K thorn and 0c -> -z thorn decays is reported, using proton -proton collision data at a center -of -mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb-1, collected with the LHCb detector between 2016 and 2018. The branching fraction ratios are measured to be Bo0c ->-K thorn thorn Bo0c ->-z thorn thorn 1/4 1/26.08 ⠂ 0.51ostat thorn ⠂ 0.40osyst thorn ⠃%; Bo0c ->-z thorn thorn Bo0c ->-z thorn thorn 1/4 1/215.81 ⠂ 0.87ostat thorn ⠂ 0.44osyst thorn ⠂ 0.16oext thorn ⠃%. In addition, using the 0c -> -z thorn decay channel, the 0c baryon mass is measured to be Mo0c thorn 1/4 2695.28 ⠂ 0.07ostat thorn ⠂ 0.27osyst thorn ⠂ 0.30oext thorn MeV; improving the precision of the previous world average by a factor of 4.
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Ikeno, N., Liang, W. H., & Oset, E. (2024). Molecular nature of the Ωc(3120) and its analogy with the Ω(2012). Phys. Rev. D, 109(5), 054023–7pp.
Abstract: We make a study of the omega c(3120) , one of the five omega c states observed by the LHCb Collaboration, which is well reproduced as a molecular state from the Xi*cK over bar and omega*c17 channels mostly. The state with JP = 3/2- decays to Xi cK over bar in the D wave, and we include this decay channel in our approach, as well as the effect of the Xi*c width. With all these ingredients, we determine the fraction of the omega c(3120) width that goes into Xi cK over bar K , which could be a measure of the Xi*cK over bar molecular component, but due to a relatively big binding, compared to its analogous omega(2012) state, we find only a small fraction of about 3%, which makes this measurement difficult with present statistics. As an alternative, we evaluate the scattering length and effective range of the Xi*c K over bar and omega*c17 channels, which, together with the binding and width of the omega c(3120) state, could give us an answer to the issue of the compositeness of this state when these magnitudes are determined experimentally, something feasible nowadays, for instance, measuring correlation functions.
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Dai, L. R., & Oset, E. (2024). Dynamical generation of the scalar f0(500), f0(980), and K0*(700) resonances in the Ds+ → K+ π+ π- reaction. Phys. Rev. D, 109(5), 054008–9pp.
Abstract: We develop a model aimed at understanding the three mass distributions of pairs of mesons in the Cabibbo-suppressed D-s(+) – K+pi(+)pi(-) decay recently measured with high statistics by the BESIII collaboration. The largest contributions to the process come from the D-s(+) -> K+ rho(0) and D-s(+) -> K*(0)pi(+) decay modes, but the D-s(+) -> K-0*(1430)pi(+) and D-s(+) -> K+ f(0) (1370) modes also play a moderate role and all of them are introduced empirically. Instead, the contribution of the f(0)(500), f(0)(980) , and K-0*(700) resonances is introduced dynamically by looking at the decay modes at the quark level, hadronizing q (q) over bar over bar pairs to give two mesons, and allowing these mesons to interact, for which we follow the chiral unitary approach, to finally produce the K+ pi(+) pi(-) final state. While the general features of the mass distributions are fairly obtained, we pay special attention to the specific effects created by the light scalar resonances, which are visible in the low mass region of the pi(+) pi(-) (f(0)(500) and K+ pi(-) K+pi-(K-0*(700)) mass distributions and a narrow peak for pi(+) pi(-) distribution corresponding to f(0)(980) excitation. The contribution of these three resonances is generated by only one parameter. We see the agreement found in these regions as further support for the nature of the light scalar states as dynamically generated from the interaction of pseudoscalar mesons.
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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. (2024). Curvature-bias corrections using a pseudomass method. J. Instrum., 19(3), P03010–22pp.
Abstract: Momentum measurements for very high momentum charged particles, such as muons from electroweak vector boson decays, are particularly susceptible to charge-dependent curvature biases that arise from misalignments of tracking detectors. Low momentum charged particles used in alignment procedures have limited sensitivity to coherent displacements of such detectors, and therefore are unable to fully constrain these misalignments to the precision necessary for studies of electroweak physics. Additional approaches are therefore required to understand and correct for these effects. In this paper the curvature biases present at the LHCb detector are studied using the pseudomass method in proton-proton collision data recorded at centre of mass energy root s = 13 TeV during 2016, 2017 and 2018. The biases are determined using Z -> mu(+)mu(-) decays in intervals defined by the data-taking period, magnet polarity and muon direction. Correcting for these biases, which are typically at the 10(-4) GeV-1 level, improves the Z -> mu(+)mu(-) mass resolution by roughly 18% and eliminates several pathological trends in the kinematic-dependence of the mean dimuon invariant mass.
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ATLAS Collaboration(Aad, G. et al), Aikot, A., Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., et al. (2024). Search for a CP-odd Higgs boson decaying into a heavy CP-even Higgs boson and a Z boson in the l+l-t(t)over-bar and ν(ν)over-barb(b)over-bar final states using 140 fb-1 of data collected with the ATLAS detector. J. High Energy Phys., 02(2), 197–56pp.
Abstract: A search for a heavy CP-odd Higgs boson, A, decaying into a Z boson and a heavy CP-even Higgs boson, H, is presented. It uses the full LHC Run 2 dataset of pp collisions at root s = 13TeV collected with the ATLAS detector, corresponding to an integrated luminosity of 140 fb(-1). The search for A -> ZH is performed in the l(+)l(-)t (t) over bar t and nu(nu) over barb (b) over bar final states and surpasses the reach of previous searches in different final states in the region with m(H) > 350 GeV and m(A) > 800 GeV. No significant deviation from the Standard Model expectation is found. Upper limits are placed on the production cross-section times the decay branching ratios. Limits with less model dependence are also presented as functions of the reconstructed m(t (t) over bar) and m(b (b) over bar) distributions in the l(+)l(-)t (t) over bar and nu(nu) over barb (b) over bar channels, respectively. In addition, the results are interpreted in the context of two-Higgs-doublet models.
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