472 research outputs found
Random-coupled Neural Network
Improving the efficiency of current neural networks and modeling them in
biological neural systems have become popular research directions in recent
years. Pulse-coupled neural network (PCNN) is a well applicated model for
imitating the computation characteristics of the human brain in computer vision
and neural network fields. However, differences between the PCNN and biological
neural systems remain: limited neural connection, high computational cost, and
lack of stochastic property. In this study, random-coupled neural network
(RCNN) is proposed. It overcomes these difficulties in PCNN's neuromorphic
computing via a random inactivation process. This process randomly closes some
neural connections in the RCNN model, realized by the random inactivation
weight matrix of link input. This releases the computational burden of PCNN,
making it affordable to achieve vast neural connections. Furthermore, the image
and video processing mechanisms of RCNN are researched. It encodes constant
stimuli as periodic spike trains and periodic stimuli as chaotic spike trains,
the same as biological neural information encoding characteristics. Finally,
the RCNN is applicated to image segmentation, fusion, and pulse shape
discrimination subtasks. It is demonstrated to be robust, efficient, and highly
anti-noised, with outstanding performance in all applications mentioned above
LHCb potential to discover long-lived new physics particles with lifetimes above 100 ps
For years, it has been believed that the main LHC detectors can only
restrictively play the role of a lifetime frontier experiment exploring the
parameter space of long-lived particles (LLPs) - hypothetical particles with
tiny couplings to the Standard Model. This paper demonstrates that the LHCb
experiment may become a powerful lifetime frontier experiment if it uses the
new Downstream algorithm reconstructing tracks that do not let hits in the LHCb
vertex tracker. In particular, for many LLP scenarios, LHCb may be as sensitive
as the proposed experiments beyond main LHC detectors for various LLP models,
including heavy neutral leptons, dark scalars, dark photons, and axion-like
particles.Comment: Matches the version accepted for the publication in EPJ
LHCb potential to discover long-lived new physics particles with lifetimes above 100 ps
For years, it has been believed that the main LHC detectors can play only a limited role of a lifetime frontier experiment exploring the parameter space of long-lived particles (LLPs)—hypothetical particles with tiny couplings to the Standard Model. This paper demonstrates that the LHCb experiment may become a powerful lifetime frontier experiment if it uses the new Downstream algorithm reconstructing tracks that do not allow hits in the LHCb vertex tracker. In particular, for many LLP scenarios, LHCb may be as sensitive as the proposed experiments beyond the main LHC detectors for various LLP models, including heavy neutral leptons, dark scalars, dark photons, and axion-like particles
LHCb potential to discover long-lived new physics particles with lifetimes above 100 ps
For years, it has been believed that the main LHC detectors can only restrictively play the role of a lifetime frontier experiment exploring the parameter space of long-lived particles (LLPs) - hypothetical particles with tiny couplings to the Standard Model. This paper demonstrates that the LHCb experiment may become a powerful lifetime frontier experiment if it uses the new Downstream algorithm reconstructing tracks that do not let hits in the LHCb vertex tracker. In particular, for many LLP scenarios, LHCb may be as sensitive as the proposed experiments beyond main LHC detectors for various LLP models, including heavy neutral leptons, dark scalars, dark photons, and axion-like particles
Impact of the high-level trigger for detecting long-lived particles at LHCb
Long-lived particles (LLPs) are very challenging to search for with current detectors and computing requirements due to their very displaced vertices. This study evaluates the ability of the trigger algorithms used in the Large Hadron Collider beauty (LHCb) experiment to detect long-lived particles and attempts to adapt them to enhance the sensitivity of this experiment to undiscovered long-lived particles. One of the challenges in the track reconstruction is to deal with the large amount of combinatorics of hits. A dedicated algorithm has been developed to cope with the large data output. When fully implemented, this algorithm would greatly increase the efficiency for any long-lived particle reconstruction in the forward region, for the Standard Model of particle physics and beyond
Observation of New Baryons in the Ξb- π+π- and Ξb0 π+π- Systems
The first observation and study of two new baryonic structures in the final state Ξb0π+π- and the confirmation of the Ξb(6100)- state in the Ξb-π+π- decay mode are reported using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb-1. In addition, the properties of the known Ξb∗0, Ξb′- and Ξb∗- resonances are measured with improved precision. The new decay mode of the Ξb0 baryon to the Ξc+ π- π+ π- final state is observed and exploited for the first time in these measurements
Search for D∗(2007)0 → μ+μ− in B− → π−μ+μ− decays
The very rare D∗(2007)0→μ+μ- decay is searched for by analysing B-→π-μ+μ- decays. The analysis uses a sample of beauty mesons produced in proton–proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 \,fb . The signal signature corresponds to simultaneous peaks in the μμ and πμμ invariant masses. No evidence for an excess of events over background is observed and an upper limit is set on the branching fraction of the decay at B(D∗(2007)0→μ+μ-)<2.6×10-8 at 90 % confidence level. This is the first limit on the branching fraction of D∗(2007)0→μ+μ- decays and the most stringent limit on D(2007) decays to leptonic final states. The analysis is the first search for a rare charm-meson decay exploiting production via beauty decays
Test of lepton flavor universality using B0 →D∗-τ+ντ decays with hadronic τ channels
The branching fraction B(B0→D∗-τ+ντ) is measured relative to that of the normalization mode B0→D∗-π+π-π+ using hadronic τ+→π+π-π+(π0)ν¯τ decays in proton-proton collision data at a center-of-mass energy of 13 TeV collected by the LHCb experiment, corresponding to an integrated luminosity of 2 fb-1. The measured ratio is B(B0→D∗-τ+ντ)/B(B0→D∗-π+π-π+)=1.70±0.10-0.10+0.11, where the first uncertainty is statistical and the second is related to systematic effects. Using established branching fractions for the B0→D∗-π+π-π+ and B0→D∗-μ+νμ modes, the lepton universality test R(D∗-)B(B0→D∗-τ+ντ)/B(B0→D∗-μ+νμ) is calculated, R(D∗-)=0.247±0.015±0.015±0.012, where the third uncertainty is due to the uncertainties on the external branching fractions. This result is consistent with the Standard Model prediction and with previous measurements
Gender differential impact of bereavement on health outcomes: evidence from the China Health and Retirement Longitudinal Study, 2011–2015
Background: Bereavement is the experience of an individual following the death of a person of significance to the individual, most often referring to the spouse. Increased morbidity, health care utilization, and mortality are known to be associated with bereavement. Given China’s growing population of older adults, there is a critical need to assess the health consequences of bereavement. Method: We use data from the China Health and Retirement Longitudinal Study to examine the impact of bereavement on mental health and quality of life among a sample of mid- and older-aged adults. We use propensity score matching to construct a matching sample and difference-in-differences method to estimate the impact of bereavement on mental health and self-assessed health. Results: We find bereavement is associated with increased depression symptoms among women (1.542 point or 0.229 standard deviations of Center for Epidemiologic Studies Depression (CES-D) 10 score) but not consistently for men over time. No statistically significant effect of bereavement on self-assessed health is found. Conclusions: Our results show a harmful impact of bereavement on mental health among older women in China and point to the need for a comprehensive policy on survivor benefits in China, particularly for rural older women
Measurement of the mass difference and relative production rate of the ωb- and Ξb- baryons
The mass difference between the ωb- and Ξb- baryons is measured using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb-1, and is found to be m(ωb-)-m(Ξb-)=248.54±0.51(stat)±0.38(syst) MeV/c2. The mass of the ωb- baryon is measured to be m(ωb-)=6045.9±0.5(stat)±0.6(syst) MeV/c2. This is the most precise determination of the ωb- mass to date. In addition, the production rate of ωb- baryons relative to that of Ξb- baryons is measured for the first time in pp collisions, using an LHCb dataset collected at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 6 fb-1. Reconstructing beauty baryons in the kinematic region 2<η<6 and pT<20 GeV/c with their decays to a J/ψ meson and a hyperon, the ratio fωb-fΞb-×B(ωb-→J/ψω-)B(Ξb-→J/ψΞ-)=0.120±0.008(stat)±0.008(syst), is obtained, where fωb- and fΞb- are the fragmentation fractions of b quarks into ωb- and Ξb- baryons, respectively, and B represents the branching fractions of their respective decays
- …