Almanza Soto, M. (2025). Design, prototyping, and test of a Highly Compact and Granular Electromagnetic Calorimeter for the LUXE experiment. Nucl. Instrum. Methods Phys. Res. A, 1080, 170679–6pp.
Abstract: The LUXE experiment will investigate the strong-field QED regime by using the interactions of high-energy electrons from the European XFEL in a powerful laser field. It will measure the production of electron-positron pairs as a function of the laser field strength, up to the non-perturbative non-linear regime. LUXE foresees a positron detection system consisting of a tracker and a granular and unprecedentedly compact silicon-tungsten electromagnetic sandwich calorimeter (ECAL-P). The ECAL-P has been designed to cope with the wide range of the expected number of positrons per bunch crossing. In addition, the energy distribution of the positrons has to be measured on top of a widely spread low-energy background. The ECAL-P is composed of tungsten absorber plates interspersed with thin sensor planes, consisting of silicon pad sensors, flexible Kapton printed circuit planes, and carbon fiber support. The sensor planes are less than 1 mm thick and will be read using dedicated front-end ASICs in 130 nm technology (FLAXE) and FPGAs for data pre-processing. GaAs sensor planes with integrated readout strips are also being considered as an alternative to silicon. Prototypes of individual sensor planes have been tested in a 5 GeV electron beam. A full compact calorimeter tower of up to 90 x 90 x 600 mm3 (15 X0) will be produced and tested in an electron beam. The design challenges, sensor characterization, prototyping, integration, commissioning, and the available results from a beam test in 2022 are discussed.
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Mandic, I. et aI., Soldevila, U., Lacasta, C., Solaz, C., & Bernabeu, J. (2025). Unusual annealing of charge collection efficiency of silicon strip detectors, ATLAS18, irradiated to high fluences with 23 GeV protons. Nucl. Instrum. Methods Phys. Res. A, 1080, 170682–4pp.
Abstract: Extensive studies were performed on highly irradiated ATLAS18 mini strip detectors to evaluate their annealing behaviour. Collected charge was measured after several steps of annealing at 60 degrees C. For detectors irradiated with neutrons or low energy protons the collected charge exhibited a beneficial effect of short-term annealing which was followed by a decrease in charge collection efficiency at longer annealing times. After irradiation with 23 GeV protons to fluences above Phi(eq) similar to 1.2 . 10(15) cm(-2), the collected charge remained unchanged or decreased after the first few tens of minutes of annealing. Edge-TCT measurements indicated that this unusual annealing behaviour is related to the double-peak electric field profile in the detector. Mixed irradiation with 23 GeV protons and neutrons to fluences matching the expected in the upgraded ATLAS experiment showed this unusual annealing effect will not impact the operation of the ITk strip detector.
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Pilsl, B., Bergauer, T., Casanova, R., Handerkas, H., Irmler, C., Kraemer, U., et al. (2025). Enhancing radiation hardness and granularity in HV-CMOS: The RD50-MPW4 sensor. Nucl. Instrum. Methods Phys. Res. A, 1080, 170752–5pp.
Abstract: The latest HV-CMOS pixel sensor developed by the former CERN-RD50-CMOS group, known as the RD50-MPW4, demonstrates competitive radiation tolerance, spatial granularity, and timing resolution – requirements for future high-energy physics experiments such as the HL-LHC and FCC. Fabricated using 150 nm CMOS process by LFoundry, it introduces several improvements over its predecessor, the RD50-MPW3, including separated power domains for reduced noise, a new backside biasing scheme, and an enhanced guard ring structure, enabling operation at bias voltages up to 800 V. Tests with non-irradiated samples achieved hit detection efficiencies exceeding 99.9 % and a spatial resolution around 16 μm. Neutron-irradiated sensors were characterized using IV measurements and beam campaigns, confirming the sensor's robustness in high-radiation environments. The results highlight ability of HV-CMOS technology to restore hit detection efficiency post-irradiation by increasing the applied bias voltage. Details of these measurements and timing performance are presented in this paper.
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Abbas, G. (2016). Right-right-left extension of the Standard Model. Mod. Phys. Lett. A, 31(19), 1650117–10pp.
Abstract: A right-right-left extension of the Standard Model is proposed. In this model, SM gauge group SU(2)(L) circle times U(1)(Y) is extended to SU(2)(L) circle times SU(2)(R) circle times SU(2)'(R) circle times SU(2)'(L) circle times U(1)(Y). The gauge symmetries SU(2)'(R), SU(2)'(L) are the mirror counterparts of the SU(2)(L) and SU(2)(R), respectively. Parity is spontaneously broken when the scalar Higgs fields acquire vacuum expectation values (VEVs) in a certain pattern. Parity is restored at the scale of SU(2)'(L). The gauge sector has a unique pattern. The scalar sector of the model is optimum, elegant and unique.
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Han, X. F., Wang, L., & Yang, J. M. (2016). Higgs pair signal enhanced in the 2HDM with two degenerate 125 GeV Higgs bosons. Mod. Phys. Lett. A, 31(31), 1650178–14pp.
Abstract: We discuss a scenario of the type-II two-Higgs- doublet model (2HDM) in which the b (b) over bar gamma gamma rate of the Higgs pair production is enhanced due to the two nearly degenerate 125 GeV Higgs bosons ( h, H). Considering various theoretical and experimental constraints, we figure out the allowed ranges of the trilinear couplings of these two Higgs bosons and calculate the signal rate of b (b) over bar gamma gamma from the productions of Higgs pairs (hh, hH, HH) at the large hadron collider (LHC). We find that in the allowed parameter space some trilinear Higgs couplings can be larger than the Standard Model (SM) value by an order and the production rate of b _ b.. can be greatly enhanced. We also consider a “decoupling” benchmark point where the light CP-even Higgs has a SM-like cubic self-coupling while other trilinear couplings are very small. With a detailed simulation on the b (b) over bar gamma gamma signal and backgrounds, we find that in such a “decoupling” scenario the hh and hH channels can jointly enhance the statistical significance to 5 sigma at 14 TeV LHC with an integrated luminosity of 3000 fb(-1).
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Pich, A., & Rodriguez-Sanchez, A. (2016). Updated determination of alpha(s)(m(tau)(2)) from tau decays. Mod. Phys. Lett. A, 31(30), 1630032–15pp.
Abstract: Using the most recent release of the ALEPH tau decay data, we present a very detailed phenomenological update of the alpha(s)(m(tau)(2)) determination. We have exploited the sensitivity to the strong coupling in many different ways, exploring several complementary methodologies. All determinations turn out to be in excellent agreement, allowing us to extract a very reliable value of the strong coupling. We find alpha((nf =3))(s)(m(tau)(2)) = 0.328 +/- 0.012 which implies alpha((nf=5))(s)(M-Z(2)) = 0.1197 +/- 0.0014. We critically revise previous work, and point out the problems flawing some recent analyses which claim slightly smaller values.
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Peinado, E., Reig, M., Srivastava, R., & Valle, J. W. F. (2020). Dirac neutrinos from Peccei-Quinn symmetry: A fresh look at the axion. Mod. Phys. Lett. A, 35(21), 2050176–9pp.
Abstract: We show that a very simple solution to the strong CP problem naturally leads to Dirac neutrinos. Small effective neutrino masses emerge from a type-I Dirac seesaw mechanism. Neutrino mass limits probe the axion parameters in regions currently inaccessible to conventional searches.
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Centelles Chulia, S., & Trautner, A. (2020). Asymmetric tri-bi-maximal mixing and residual symmetries. Mod. Phys. Lett. A, 35(35), 2050292–15pp.
Abstract: Asymmetric tri-bi-maximal mixing is a recently proposed, grand unified theory (GUT) based, flavor mixing scheme. In it, the charged lepton mixing is fixed by the GUT connection to down-type quarks and a T-13 flavor symmetry, while neutrino mixing is assumed to be tri-bi-maximal (TBM) with one additional free phase. Here we show that this additional free phase can be fixed by the residual flavor and CP symmetries of the effective neutrino mass matrix. We discuss how those residual symmetries can be unified with T-13 and identify the smallest possible unified flavor symmetries, namely (Z(13)xZ(13))(sic)D-12 and (Z(13)xZ(13))(sic)S-4. Sharp predictions are obtained for lepton mixing angles, CP violating phases and neutrinoless double beta decay.
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Baker, M. J., Bordes, J., Hong-Mo, C., & Tsun, T. S. (2011). Mass Hierarchy, Mixing, CP-Violation And Higgs Decay – Or Why Rotation Is Good For Us. Int. J. Mod. Phys. A, 26(13), 2087–2124.
Abstract: The idea of a rank-one rotating mass matrix (R2M2) is reviewed detailing how it leads to ready explanations both for the fermion mass hierarchy and for the distinctive mixing patterns between up and down fermion states, which can be and have been tested against experiment and shown to be fully consistent with existing data. Further, R2M2 is seen to offer, as by-products: (i) a new solution to the strong CP problem in QCD by linking the theta-angle there to the Kobayashi-Maskawa CP-violating phase in the CKM matrix, and (ii) some novel predictions of possible anomalies in Higgs decay observable in principle at the LHC. A special effort is made to answer some questions raised.
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Bordes, J., Chan, H. M., & Tsun, T. S. (2010). A solution to the strong CP problem transforming the theta angle to the KM CP-violating phase. Int. J. Mod. Phys. A, 25(32), 5897–5911.
Abstract: It is shown that in the scheme with a rotating fermion mass matrix (i.e. one with a scale-dependent orientation in generation space) suggested earlier for explaining fermion mixing and mass hierarchy, the theta angle term in the QCD action of topological origin can be eliminated by chiral transformations, while giving still nonzero masses to all quarks. Instead, the effects of such transformations get transmitted by the rotation to the CKM matrix as the KM phase giving, for theta of order unity, a Jarlskog invariant typically of order 10(-5), as experimentally observed. Strong and weak CP violations appear then as just two facets of the same phenomenon.
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