Search results for "Lepton"
showing 10 items of 1512 documents
PRODUCTION-RATE AND DECAY LIFETIME MEASUREMENTS OF B(S)0 MESONS AT LEP USING D(S) AND PHI MESONS
1994
The study of the properties of inclusive production of Ds mesons and of events in which a φ{symbol} and a muon are present in the same jet provides two independent measurements of the probability, fs w, for a heavy quark to hadronize into a strange B or D meson. The data sample analysed corresponds to 243,000 hadronic Z0 decays. The combined value of these measurements is fs w=0.19±0.06±0.08. From the flight distance distributions of Ds and of (φ{symbol}-lepton) secondary vertices, with the lepton emitted at high transverse momentum relative to the jet axis, two values are obtained for the Bs 0 meson lifetime. Combining these measurements with a previous result based on the study of Ds-μ ev…
EPPS16: Nuclear parton distributions with LHC data
2017
We introduce a global analysis of collinearly factorized nuclear parton distribution functions (PDFs) including, for the first time, data constraints from LHC proton-lead collisions. In comparison to our previous analysis, EPS09, where data only from charged-lepton-nucleus deep inelastic scattering (DIS), Drell-Yan (DY) dilepton production in proton-nucleus collisions and inclusive pion production in deuteron-nucleus collisions were the input, we now increase the variety of data constraints to cover also neutrino-nucleus DIS and low-mass DY production in pion-nucleus collisions. The new LHC data significantly extend the kinematic reach of the data constraints. We now allow much more freedom…
Search for composite and exotic fermions at LEP 2
1999
A search for unstable heavy fermions with the DELPHI detector at LEP is reported. Sequential and non-canonical leptons, as well as excited leptons and quarks, are considered. The data analysed correspond to an integrated luminosity of about 48~pb$^{-1}$ at an $e^+e^-$ centre-of-mass energy of 183~GeV and about 20~pb$^{-1}$ equally shared between the centre-of-mass energies of 172~GeV and 161~GeV. The search for pair-produced new leptons establishes 95\% confidence level mass limits in the region between 70~GeV/$c^2$ and 90~GeV/$c^2$, depending on the channel. The search for singly produced excited leptons and quarks establishes upper limits on the ratio of the coupling of the excited fermio…
Neutrino Mass Ordering from Oscillations and Beyond: 2018 Status and Future Prospects
2018
The ordering of the neutrino masses is a crucial input for a deep understanding of flavor physics, and its determination may provide the key to establish the relationship among the lepton masses and mixings and their analogous properties in the quark sector. The extraction of the neutrino mass ordering is a data-driven field expected to evolve very rapidly in the next decade. In this review, we both analyze the present status and describe the physics of subsequent prospects. Firstly, the different current available tools to measure the neutrino mass ordering are described. Namely, reactor, long-baseline (accelerator and atmospheric) neutrino beams, laboratory searches for beta and neutrinol…
Gravitational Imprints of Flavor Hierarchies
2020
The mass hierarchy among the three generations of quarks and charged leptons is one of the greatest mysteries in particle physics. In various flavor models, the origin of this phenomenon is attributed to a series of hierarchical spontaneous symmetry breakings, most of which are beyond the reach of particle colliders. We point out that the observation of a multi-peaked stochastic gravitational wave signal from a series of cosmological phase transitions could well be a unique probe of the mechanism behind flavor hierarchies. To illustrate this point, we show how near future ground- and space-based gravitational wave observatories could detect up to three peaks in the recently proposed $PS^3$ …
Flavour Symmetries and SUSY Soft Breaking in the LHC Era
2007
The so-called supersymmetric flavour problem does not exist in isolation to the Standard Model flavour problem. We show that a realistic flavour symmetry can simultaneously solve both problems without ad hoc modifications of the SUSY model. Furthermore, departures from the SM expectations in these models can be used to discriminate among different possibilities. In particular we present the expected values for the electron EDM in a flavour model solving the supersymmetric flavour and CP problems.
Top mass reconstruction in ATLAS
2011
The top-quark mass is a fundamental parameter of the Standard Model. After the discovery of the top quark, the measurements of its properties were of substantial interest. Within the framework of the SM, the top-quark mass can be used in combination with other electroweak precision measurements to constrain the mass of the yet unobserved Higgs boson.\nIn the new era of the Large Hadron Collider (LHC), the first top quarks have been produced in Europe in proton-proton collisions at a center-of-mass energy of 7~TeV. The top-quark mass measurement of ATLAS in the so called lepton+jets channel with 35~pb$^{-1}$ integrated luminosity will be presented. In this early data-taking period the larges…
Searches for sleptons and squarks in e(+)e(-) collisions at 189 GeV
1999
The data collected at a centre-of-mass energy of 188.6 GeV by ALEPH at LEP, corresponding to an integrated luminosity of 173.6 pb$^{-1}$, are analysed in a search for the scalar partners of quarks and leptons predicted in supersymmetric models. No evidence for any such particles was found in the decay channels $\sle \to \ell \chi$, $\stop \rightarrow \mathrm{c}\neu$, $\stop \rightarrow \mathrm{b}\ell\snu$, $\sbot \rightarrow \mathrm{b}\neu$, and $\mathrm{\tilde{q}} \rightarrow \mathrm{q}\neu$. Improved mass lower limits have been obtained in the framework of the Minimal Supersymmetric Standard Model.
Extended van Royen-Weisskopf formalism for lepton-antilepton meson decay widths within non-relativistic quark models
2001
The classical van Royen-Weisskopf formula for the decay width of a meson into a lepton-antilepton pair is modified in order to include non-zero quark momentum contributions within the meson as well as relativistic effects. Besides, a phenomenological electromagnetic density for quarks is introduced. The meson wave functions are obtained from two different models: a chiral constituent quark model and a quark potential model including instanton effects. The modified van Royen-Weisskopf formula is found to improve systematically the results for the widths, giving an overall good description of all known decays.
Search for excited leptons in proton-proton collisions ats=7 TeVwith the ATLAS detector
2012
The ATLAS detector is used to search for excited leptons in the electromagnetic radiative decay channel l* -> l gamma. Results are presented based on the analysis of pp collisions at a center-of ...