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CDF Collaboration(Aaltonen, T. et al), & Cabrera, S. (2011). Search for a Very Light CP-Odd Higgs Boson in Top Quark Decays from p p-bar Collisions at sqrt(s)=1.96 TeV. Phys. Rev. Lett., 107(3), 031801–8pp.
Abstract: We present the results of a search for a very light CP-odd Higgs boson a(1)(0) originating from top quark decays t -> H(+/-)b -> W(+/-(*)) a(1)(0)b, and subsequently decaying into tau(+)tau(-). Using a data sample corresponding to an integrated luminosity of 2.7 fb(-1) collected by the CDF II detector in p (p) over bar collisions at 1.96 TeV, we perform a search for events containing a lepton, three or more jets, and an additional isolated track with transverse momentum in the range 3 to 20 GeV/c. Observed events are consistent with background sources, and 95% C.L. limits are set on the branching ratio of t -> H(+/-)b for various masses of H(+/-) and a(1)(0).
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fernandez Martinez, P., Ferrer, A., et al. (2015). Search for a Heavy Neutral Particle Decaying to e mu, e tau, or μtau in pp Collisions at root s=8 TeV with the ATLAS Detector. Phys. Rev. Lett., 115(3), 031801–18pp.
Abstract: This Letter presents a search for a heavy neutral particle decaying into an opposite-sign different-flavor dilepton pair, e(+/-) mu(-/+), e(+/-) tau(-/+), or mu(+/-) tau(-/+) using 20.3 fb(-1) of pp collision data at root s = 8 TeV collected by the ATLAS detector at the LHC. The numbers of observed candidate events are compatible with the standard model expectations. Limits are set on the cross section of new phenomena in two scenarios: the production of (nu) over tilde (tau) in R-parity-violating supersymmetric models and the production of a lepton-flavor-violating Z' vector boson.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2019). First Observation of the Radiative Decay Lambda(0 )(b)-> Lambda gamma. Phys. Rev. Lett., 123(3), 031801–11pp.
Abstract: The radiative decay Lambda(0 )(b)-> Lambda gamma is observed for the first time using a data sample of proton-proton collisions corresponding to an integrated luminosity of 1.7 fb(-1) collected by the LHCb experiment at a center-of-mass energy of 13 TeV. Its branching fraction is measured exploiting the B-0 -> K*(0)gamma decay as a normalization mode and is found to be B(Lambda(0 )(b)-> Lambda gamma) = (7.1 +/- 1.5 +/- 0.6 +/- 0.7) x 10(-6), where the quoted uncertainties arc statistical, systematic, and systematic from external inputs, respectively. This is the first observation of a radiative decay of a beauty baryon.
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LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., et al. (2020). Observation of Several Sources of CP Violation in B+ -> pi(+)pi(+)pi(-) Decays. Phys. Rev. Lett., 124(3), 031801–11pp.
Abstract: Observations are reported of different sources of CP violation from an amplitude analysis of B+ -> pi(+)pi(+)pi(-) decays, based on a data sample corresponding to an integrated luminosity of 3 fb(-1) of pp collisions recorded with the LHCb detector. A large CP asymmetry is observed in the decay amplitude involving the tensor f(2)(1270) resonance, and in addition significant CP violation is found in the pi(+)pi S- wave at low invariant mass. The presence of CP violation related to interference between the pi(+)pi S- wave and the P wave B+ -> rho(770)(0)pi(+) amplitude is also established; this causes large local asymmetries but cancels when integrated over the phase space of the decay. The results provide both qualitative and quantitative new insights into CP -violation effects in hadronic B decays.
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LHCb Collaboration(Aaij, R. et al), Martinez-Vidal, F., Oyanguren, A., Ruiz Valls, P., & Sanchez Mayordomo, C. (2015). Measurement of CP Violation in B-0 -> J/psi K-S(0) Decays. Phys. Rev. Lett., 115(3), 031601–9pp.
Abstract: Measurements are presented of the CP violation observables S and C in the decays of B-0 and (B) over bar (0) mesons to the J/psi K-S(0) final state. The data sample corresponds to an integrated luminosity of 3.0 fb(-1) collected with the LHCb experiment in proton-proton collisions at center-of-mass energies of 7 and 8 TeV, and contains a total of 41 560 selected B-0 and (B) over bar (0) decays. The analysis of the time evolution of these decays yields S = 0.731 +/- 0.035(stat) +/- 0.020(syst) and C = -0.038 +/- 0.032(stat) +/- 0.005(syst). In the standard model, S equals sin(2 beta) to a good level of precision. The values are consistent with the current world averages and with the standard model expectations.
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Boiron, D., Fabbri, A., Larre, P. E., Pavloff, N., Westbrook, C. I., & Zin, P. (2015). Quantum Signature of Analog Hawking Radiation in Momentum Space. Phys. Rev. Lett., 115(2), 025301–5pp.
Abstract: We consider a sonic analog of a black hole realized in the one-dimensional flow of a Bose-Einstein condensate. Our theoretical analysis demonstrates that one-and two-body momentum distributions accessible by present-day experimental techniques provide clear direct evidence (i) of the occurrence of a sonic horizon, (ii) of the associated acoustic Hawking radiation, and (iii) of the quantum nature of the Hawking process. The signature of the quantum behavior persists even at temperatures larger than the chemical potential.
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Morales, A. I., Algora, A., Molina, F., & Rubio, B. (2014). Half-Life Systematics across the N=126 Shell Closure: Role of First-Forbidden Transitions in the beta Decay of Heavy Neutron-Rich Nuclei. Phys. Rev. Lett., 113(2), 022702–5pp.
Abstract: This Letter reports on a systematic study of beta-decay half-lives of neutron-rich nuclei around doubly magic Pb-208. The lifetimes of the 126-neutron shell isotone Pt-204 and the neighboring Ir200-202, Pt-203, Au-204 are presented together with other 19 half-lives measured during the “stopped beam” campaign of the rare isotope investigations at GSI collaboration. The results constrain the main nuclear theories used in calculations of r-process nucleosynthesis. Predictions based on a statistical macroscopic description of the first-forbidden beta strength reveal significant deviations for most of the nuclei with N < 126. In contrast, theories including a fully microscopic treatment of allowed and first-forbidden transitions reproduce more satisfactorily the trend in the measured half-lives for the nuclei in this region, where the r-process pathway passes through during beta decay back to stability.
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Estienne, M., Fallot, M., Algora, A., Briz-Monago, J., Bui, V. M., Cormon, S., et al. (2019). Updated Summation Model: An Improved Agreement with the Daya Bay Antineutrino Fluxes. Phys. Rev. Lett., 123(2), 022502–6pp.
Abstract: A new summation method model of the reactor antineutrino energy spectrum is presented. It is updated with the most recent evaluated decay databases and with our total absorption gamma-ray spectroscopy measurements performed during the last decade. For the first time, the spectral measurements from the Daya Bay experiment are compared with the antineutrino energy spectrum computed with the updated summation method without any renormalization. The results exhibit a better agreement than is obtained with the Huber-Mueller model in the 2-5 MeV range, the region that dominates the detected flux. A systematic trend is found in which the antineutrino flux computed with the summation model decreases with the inclusion of more pandemonium-free data. The calculated flux obtained now lies only 1.9% above that detected in the Daya Bay experiment, a value that may be reduced with forthcoming new pandemonium-free data, leaving less room for a reactor anomaly. Eventually, the new predictions of individual antineutrino spectra for the U-235, Pu-239, Pu-241, and U-238 are used to compute the dependence of the reactor antineutrino spectral shape on the fission fractions.
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n_TOF Collaboration(Lederer, C. et al), Domingo-Pardo, C., Giubrone, G., & Tain, J. L. (2013). Neutron Capture Cross Section of Unstable Ni-63: Implications for Stellar Nucleosynthesis. Phys. Rev. Lett., 110(2), 022501–5pp.
Abstract: The Ni-63(n, gamma) cross section has been measured for the first time at the neutron time-of-flight facility n_TOF at CERN from thermal neutron energies up to 200 keV. In total, capture kernels of 12 (new) resonances were determined. Maxwellian averaged cross sections were calculated for thermal energies from kT = 5-100 keV with uncertainties around 20%. Stellar model calculations for a 25M(circle dot) star show that the new data have a significant effect on the s-process production of Cu-63, Ni-64, and Zn-64 in massive stars, allowing stronger constraints on the Cu yields from explosive nucleosynthesis in the subsequent supernova.
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Xu, Z. Y. et al, Algora, A., & Morales, A. I. (2023). 133In: A Rosetta Stone for Decays of r-Process Nuclei. Phys. Rev. Lett., 131(2), 022501–6pp.
Abstract: The beta decays from both the ground state and a long-lived isomer of In-133 were studied at the ISOLDE Decay Station (IDS). With a hybrid detection system sensitive to beta,gamma, and neutron spectroscopy, the comparative partial half-lives (log ft) have been measured for all their dominant beta-decay channels for the first time, including a low-energy Gamow-Teller transition and several first-forbidden (FF) transitions. Uniquely for such a heavy neutron-rich nucleus, their beta decays selectively populate only a few isolated neutron unbound states in Sn-133. Precise energy and branching-ratio measurements of those resonances allow us to benchmark beta-decay theories at an unprecedented level in this region of the nuclear chart. The results show good agreement with the newly developed large-scale shell model (LSSM) calculations. The experimental findings establish an archetype for the beta decay of neutron-rich nuclei southeast of Sn-132 and will serve as a guide for future theoretical development aiming to describe accurately the key beta decays in the rapid-neutron capture (r-) process.
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