Montesinos, V., Albaladejo, M., Nieves, J., & Tolos, L. (2024). Charge-conjugation asymmetry and molecular content: The Ds0*(2317)± in matter. Phys. Lett. B, 853, 138656–10pp.
Abstract: We analyze the modifications that a dense nuclear medium induces in the D-s0*(2317)(+/-) and D-s1(2460)(+/-). In the vacuum, we consider them as isoscalar D-(*K-) and (D) over bar (()*())(K) over bar S-wave bound states, which are dynamically generated from effective interactions that lead to different Weinberg compositeness scenarios. Matter effects are incorporated through the two-meson loop functions, taking into account the self energies that the D-(*()), (D) over bar (()*()), K, and (K) over bar develop when embedded in a nuclear medium. Although particle-antiparticle [D-s0,s1(()*())(2317,2460)(+) versus D-s0,s1(()*())(2317,2460)(-)] lineshapes are the same in vacuum, we find extremely different density patterns in matter. This charge-conjugation asymmetry mainly stems from the very different kaon and antikaon interaction with the nucleons of the dense medium. We show that the in-medium lineshapes found for these resonances strongly depend on their D-(*()), K/(D) over bar (()*()), K molecular content, and discuss how this novel feature can be used to better determine/constrain the inner structure of these exotic states.
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Bhattacharya, S., Mondal, N., Roshan, R., & Vatsyayan, D. (2024). Leptogenesis, dark matter and gravitational waves from discrete symmetry breaking. J. Cosmol. Astropart. Phys., 06(6), 029–25pp.
Abstract: We analyse a model that connects the neutrino sector and the dark sector of the universe via a mediator 41., stabilised by a discrete Z4 symmetry that breaks to a remnant Z2 upon 41. acquiring a non -zero vacuum expectation value (v phi). The model accounts for the observed baryon asymmetry of the universe via additional contributions to the canonical Type -I leptogenesis. The Z4 symmetry breaking scale (v phi) in the model not only establishes a connection between the neutrino sector and the dark sector, but could also lead to gravitational wave signals that are within the reach of current and future experimental sensitivities.
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Pich, A., Solomonidi, E., & Vale Silva, L. (2023). Final-state interactions in the CP asymmetries of charm-meson two-body decays. Phys. Rev. D, 108, 036026–25pp.
Abstract: Urgent theoretical progress is needed in order to provide an estimate in the Standard Model of the recent measurement by LHCb of direct CP violation in charm-meson two-body decays. Rescattering effects must be taken into account for a meaningful theoretical description of the amplitudes involved in such category of observables, as signaled by the presence of large strong phases. We discuss the computation of the latter effects based on a two-channel coupled dispersion relation, which exploits isospin-zero phase shifts and inelasticity parametrizations of data coming from the rescattering processes ππ→ππ, πK→πK, and ππ→K¯K. The determination of the subtraction constants of the dispersive integrals relies on the leading contributions to the transition amplitudes from the 1/NC counting, where NC is the number of QCD colors. Furthermore, we use the measured values of the branching ratios to help in selecting the nonperturbative inputs in the isospin limit, from which we predict values for the CP asymmetries. We find that the predicted level of CP violation is much below the experimental value.
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Nacher, E., Briz, J. A., Nerio, A. N., Perea, A., Tavora, V. G., Tengblad, O., et al. (2024). Characterization of a novel proton-CT scanner based on Silicon and LaBr3(Ce) detectors. Eur. Phys. J. Plus, 139(5), 404–9pp.
Abstract: Treatment planning systems at proton-therapy centres entirely use X-ray computed tomography (CT) as primary imaging technique to infer the proton treatment doses to tumour and healthy tissues. However, proton stopping powers in the body, as derived from X-ray images, suffer from important proton-range uncertainties. In order to reduce this uncertainty in range, one could use proton-CT images instead. The main goal of this work is to test the capabilities of a newly-developed proton-CT scanner, based on the use of a set of tracking detectors and a high energy resolution scintillator for the residual energy of the protons. Different custom-made phantoms were positioned at the field of view of the scanner and were irradiated with protons at the CCB proton-therapy center in Krakow. We measured with the phantoms at different angles and produced sinograms that were used to obtain reconstructed images by Filtered Back-Projection. The obtained images were used to determine the capabilities of our scanner in terms of spatial resolution and proton Relative Stopping Power (RSP) mapping and validate its use as proton-CT scanner. The results show that the scanner can produce medium-high quality images, with spatial resolution better than 2 mm in radiography, below 3 mm in tomography and resolving power in the RSP comparable to other state-of-the-art pCT scanners.
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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). Electron and photon energy calibration with the ATLAS detector using LHC Run 2 data. J. Instrum., 19(2), P02009–58pp.
Abstract: This paper presents the electron and photon energy calibration obtained with the ATLAS detector using 140 fb-1 of LHC proton -proton collision data recorded at -Js = 13 TeV between 2015 and 2018. Methods for the measurement of electron and photon energies are outlined, along with the current knowledge of the passive material in front of the ATLAS electromagnetic calorimeter. The energy calibration steps are discussed in detail, with emphasis on the improvements introduced in this paper. The absolute energy scale is set using a large sample of Z -boson decays into electron -positron pairs, and its residual dependence on the electron energy is used for the first time to further constrain systematic uncertainties. The achieved calibration uncertainties are typically 0.05% for electrons from resonant Z -boson decays, 0.4% at ET – 10 GeV, and 0.3% at ET – 1 TeV; for photons at ET <^>' 60 GeV, they are 0.2% on average. This is more than twice as precise as the previous calibration. The new energy calibration is validated using .11tfr -, ee and radiative Z -boson decays.
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ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., Cabrera Urban, S., et al. (2024). Study of Z → llγ decays at √s=8 TeV with the ATLAS detector. Eur. Phys. J. C, 84(2), 195–29pp.
Abstract: This paper presents a study of Z -> ll gamma decays with the ATLAS detector at the Large Hadron Collider. The analysis uses a proton-proton data sample corresponding to an integrated luminosity of 20.2 fb(-1) collected at a centre-of-mass energy root s = 8 TeV. Integrated fiducial cross-sections together with normalised differential fiducial cross-sections, sensitive to the kinematics of final-state QED radiation, are obtained. The results are found to be in agreement with state-of-the-art predictions for final-state QED radiation. First measurements of Z -> ll gamma gamma decays are also reported.
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Bates, R. L. et al, Bernabeu Verdu, J., Civera, J. V., Gonzalez, F., Lacasta, C., & Sanchez, J. (2012). The ATLAS SCT grounding and shielding concept and implementation. J. Instrum., 7, P03005.
Abstract: This paper describes the design and implementation of the grounding and shielding system for the ATLAS SemiConductor Tracker (SCT). The mitigation of electromagnetic interference and noise pickup through power lines is the critical design goal as they have the potential to jeopardize the electrical performance. We accomplish this by adhering to the ATLAS grounding rules, by avoiding ground loops and isolating the different subdetectors. Noise sources are identified and design rules to protect the SCT against them are described. A rigorous implementation of the design was crucial to achieve the required performance. This paper highlights the location, connection and assembly of the different components that affect the grounding and shielding system: cables, filters, cooling pipes, shielding enclosure, power supplies and others. Special care is taken with the electrical properties of materials and joints. The monitoring of the grounding system during the installation period is also discussed. Finally, after connecting more than four thousand SCT modules to all of their services, electrical, mechanical and thermal within the wider ATLAS experimental environment, dedicated tests show that noise pickup is minimised.
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ATLAS Collaboration(Aad, G. et al), Amos, K. R., Aparisi Pozo, J. A., Bailey, A. J., Bouchhar, N., Cabrera Urban, S., et al. (2024). Observation of WZγ Production in pp Collisions at √s=13 TeV with the ATLAS Detector. Phys. Rev. Lett., 132(2), 021802–21pp.
Abstract: This Letter reports the observation of WZ gamma production and a measurement of its cross section using 140.1 +/- 1.2 fb(-1) of proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the bosons decaying leptonically, pp -> WZ gamma -> l'(perpendicular to)nu l(+) l(-)gamma (l(')(+) = e, mu), is measured in a fiducial phasespace region defined such that the leptons and the photon have high transverse momentum and the photon is isolated. The cross section is found to be 2.01 +/- 0.30(stat) +/- 0.16(syst) fb. The corresponding standard model predicted cross section calculated at next-to-leading order in perturbative quantum chromodynamics and at leading order in the electroweak coupling constant is 1.50 +/- 0.06 fb. The observed significance of the WZ gamma signal is 6.3 sigma, compared with an expected significance of 5.0 sigma.
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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. (2023). Measurement of the cross-sections of the electroweak and total production of a Zγ pair in association with two jets in pp collisions at √s= 13 TeV with the ATLAS detector. Phys. Lett. B, 846, 138222–30pp.
Abstract: This Letter presents the measurement of the fiducial and differential cross-sections of the electroweak production of a Zγ pair in association with two jets. The analysis uses 140 fb−1 of LHC proton-proton collision data taken at s√=13 TeV recorded by the ATLAS detector during the years 2015-2018. Events with a Z boson candidate decaying into either an e+e− or μ+μ− pair, a photon and two jets are selected. The electroweak component is extracted by requiring a large dijet invariant mass and a large rapidity gap between the two jets and is measured with an observed and expected significance well above five standard deviations. The fiducial pp→Zγjj cross-section for the electroweak production is measured to be 3.6 ± 0.5 fb. The total fiducial cross-section that also includes contributions where the jets arise from strong interactions is measured to be 16.8+2.0−1.8 fb. The results are consistent with the Standard Model predictions. Differential cross-sections are also measured using the same events and are compared with parton-shower Monte Carlo simulations. Good agreement is observed between data and predictions.
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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). Study of High-Transverse-Momentum Higgs Boson Production in Association with a Vector Boson in the qqbb Final State with the ATLAS Detector. Phys. Rev. Lett., 132(13), 131802–23pp.
Abstract: This Letter presents the first study of Higgs boson production in association with a vector boson (V = W or Z) in the fully hadronic qqbb final state using data recorded by the ATLAS detector at the LHC in ffiffiproton-proton collisions at root root s= 13 TeV and corresponding to an integrated luminosity of 137fb(-1). The vector bosons and Higgs bosons are each reconstructed as large-radius jets and tagged using jet substructure techniques. Dedicated tagging algorithms exploiting b-tagging properties are used to identify jets consistent with Higgs bosons decaying into b (b) over bar. Dominant backgrounds from multijet production are determined directly from the data, and a likelihood fit to the jet mass distribution of Higgs boson candidates is used to extract the number of signal events. The VH production cross section is measured inclusively and differentially in several ranges of Higgs boson transverse momentum: 250-450, 450-650, and greater than 650 GeV. The inclusive signal yield relative to the standard model expectation is observed to be μ= 1.4(-0.9)(+1.0) and the corresponding cross section is 3.1 +/- 1.3(stat)(-1.4)(+1.8) (syst) pb.
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