Motivated by models proposed to explain Standard Model anomalies, and the unprecedented τ+τ− data to be collected by the Belle II experiment during the next years, we study the kinematics of tau pair ...decays and propose a new method to search for lepton flavor violating processes in tau lepton decays to invisible beyond Standard Model particles, such as τ → ℓα, where ℓ is either an electron or a muon, and α is a massive particle that escapes undetected. The new method improves by one order of magnitude the expected upper limit on the τ → ℓα production in 3 × 1 prong tau decays and establishes the possibility of performing this search in 1 × 1 prong tau decays which has not been previously considered.
This work shows how it is possible to reconstruct SuperKEKB’s beam parameters using a Neural Network with beamstrahlung signal from the Large Angle Beamstrahlung Monitor (LABM) as input. We describe ...the device, the model, and discuss the results.
Cosmic Bose dark matter Rodríguez-Montoya, I.; Pérez-Lorenzana, A.; De La Cruz-Burelo, E. ...
Physical review. D, Particles, fields, gravitation, and cosmology,
01/2013, Letnik:
87, Številka:
2
Journal Article
Recenzirano
Odprti dostop
It is known that cold and hot dark matter imprint opposed effects on the cosmological observables; naturally, it is often thought that they should be made of different kinds of particles. We point ...out, however, that a Bose-Einstein condensate could be the source of both components. In this framework, the mass and temperature constraints on hot dark matter contain fundamental information of cold dark matter. We discuss two scenarios: a gas made of bosons and a gas made of boson-antiboson pairs. We obtain constraints on the bosonic dark matter parameters from cosmological data and test the idea by probing the condition on the critical temperature of condensation, including a forecast for the Planck mission. We find that the bosonic dark matter picture is consistent with data in the boson scenario, while the boson-antiboson scenario might be increasingly interesting for future data surveys.
The 31st Annual Meeting of the Division of Particles and Fields (DPyC) of the Mexican Physical Society was held at the José Ádem Auditorium in Cinvestav-IPN, Mexico City, Mexico, on 24-26 May 2017. ...We are extremely glad to have had a record of 180 participants attending the meeting, in which 82 presentations (39 posters and 53 talks including 40 contributed, 12 invited and a closing talk) were given. These numbers and the unquestionable scientific quality of the research work presented show the success of this meeting. In the days immediately before the meeting (22-23 May 2017) we organized a Tau Physics mini-Workshop, which can be considered the third edition of a series started in Krakow 1, 2, and where we had 12 invited seminars fostering discussions between the local Community working on Tau Physics and the invited foreign speakers, who participated in our national meeting as well. All presenters of both meetings were invited to contribute and roughly half of them accepted. We thank them for this effort, which made these proceedings possible.
We report the first search for a non-standard-model resonance decaying into $\tau$ pairs in $e^{+}e^{-}\rightarrow \mu^{+}\mu^{-} \tau^+\tau^-$ events in the 3.6-10 GeV/$c^{2}$ mass range. We use a ...62.8 fb$^{-1}$ sample of $e^+e^-$ collisions collected at a center-of-mass energy of 10.58 GeV by the Belle II experiment at the SuperKEKB collider. The analysis probes three different models predicting a spin-1 particle coupling only to the heavier lepton families, a Higgs-like spin-0 particle that couples preferentially to charged leptons (leptophilic scalar), and an axion-like particle, respectively. We observe no evidence for a signal and set exclusion limits at 90% confidence level on the product of cross section and branching fraction into $\tau$ pairs, ranging from 0.7 fb to 24 fb, and on the couplings of these processes. We obtain world-leading constraints on the couplings for the leptophilic scalar model for masses above 6.5 GeV/$c^2$ and for the axion-like particle model over the entire mass range.
We present various properties of the production of the X(3872) and ψ(2S) states based on 10.4 fb−1 collected by the D0 experiment in Tevatron pp collisions at √s = 1.96 TeV. For both states, we ...measure the nonprompt fraction fNP of the inclusive production rate due to decays of b-flavored hadrons. We find the fNP values systematically below those obtained at the LHC. The fNP fraction for ψ(2S) increases with transverse momentum, whereas for the X(3872) it is constant within large uncertainties, in agreement with the LHC results. The ratio of prompt to nonprompt ψ(2S) production, (1 − fNP)=fNP, decreases only slightly going from the Tevatron to the LHC, but for the X(3872), this ratio decreases by a factor of about 3. We test the soft-pion signature of the X(3872) modeled as a weakly bound charm-meson pair by studying the production of the X(3872) as a function of the kinetic energy of the X(3872) and the pion in the X(3872)π center-of-mass frame. For a subsample consistent with prompt production, the results are incompatible with a strong enhancement in the production of the X(3872) at the small kinetic energy of the X(3872) and the π in the X(3872)π center-of-mass frame expected for the X þ soft-pion production mechanism. For events consistent with being due to decays of b hadrons, there is no significant evidence for the soft-pion effect, but its presence at the level expected for the binding energy of 0.17 MeV and the momentum scale Λ ¼ M(π) is not ruled out.
We present the latest results from the DØ experiment on the properties of excited and heavy b-hadrons. DØ collaboration has measured the Ab lifetime in semileptonic decays as well as in a fully ...reconstructed decay channel. In addition, the first direct observation of the Ξb− baryon is reported.
We study the processes e^{+}e^{-}→ωχ_{bJ}(1P) (J=0, 1, or 2) using samples at center-of-mass energies sqrts=10.701, 10.745, and 10.805 GeV, corresponding to 1.6, 9.8, and 4.7 fb^{-1} of integrated ...luminosity, respectively. These data were collected with the Belle II detector during special operations of the SuperKEKB collider above the ϒ(4S) resonance. We report the first observation of ωχ_{bJ}(1P) signals at sqrts=10.745 GeV. By combining Belle II data with Belle results at sqrts=10.867 GeV, we find energy dependencies of the Born cross sections for e^{+}e^{-}→ωχ_{b1,b2}(1P) to be consistent with the shape of the ϒ(10753) state. These data indicate that the internal structures of the ϒ(10753) and ϒ(10860) states may differ. Including data at sqrts=10.653 GeV, we also search for the bottomonium equivalent of the X(3872) state decaying into ωϒ(1S). No significant signal is observed for masses between 10.45 and 10.65 GeV/c^{2}.
Measurement of the Λ_{c}^{+} Lifetime Ahmed, H; Ahn, J K; Aloisio, A ...
Physical review letters,
2023-Feb-17, 20230217, Letnik:
130, Številka:
7
Journal Article
Recenzirano
An absolute measurement of the Λ_{c}^{+} lifetime is reported using Λ_{c}^{+}→pK^{-}π^{+} decays in events reconstructed from data collected by the Belle II experiment at the SuperKEKB ...asymmetric-energy electron-positron collider. The total integrated luminosity of the data sample, which was collected at center-of-mass energies at or near the ϒ(4S) resonance, is 207.2 fb^{-1}. The result, τ(Λ_{c}^{+})=203.20±0.89±0.77 fs, where the first uncertainty is statistical and the second systematic, is the most precise measurement to date and is consistent with previous determinations.
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