Search results for "event"
showing 10 items of 4065 documents
Event plane determination with the new ALICE FIT detector
2021
During the on-going second long shutdown of LHC, the forward detectors of the ALICE experiment are implementing an extensive upgrade. In particular, a new Fast Interaction Trigger (FIT) has been designed and built. It consists of three sub-detector systems delivering a broad range of online functionalities, and an essential input for event characterization and physics analysis. For instance, FIT will deliver the precise collision time for the TOF-based particle identification, provide the centrality and the event plane information, and measure the cross section of diffractive processes. This note will discuss usage of FIT in the event plane determination during Run 3. A simulated event plan…
Search for Neutral, Long-Lived Particles Decaying into Two Muons inpp¯Collisions ats=1.96 TeV
2006
We present a search for a neutral particle, pair-produced in p-pbar collisions at sqrt(s)=1.96 TeV, which decays into two muons and lives long enough to travel at least 5 cm before decaying. The analysis uses ~380 pb^-1 of data recorded with the D0 detector. The background is estimated to be about one event. No candidates are observed, and limits are set on the pair production cross section times branching fraction into dimuons + X for such particles. For a mass of 10 GeV and lifetime of 4x10^-11 s, we exclude values greater than 0.14 pb (95% C.L.). These results are used to limit the interpretation of NuTeV's excess of di-muon events.
The Mu3e experiment
2021
The experiment aims for a single event sensitivity of 2\cdot 10^{-15}2⋅10−15 on the charged lepton flavour violating \mu^+\rightarrow e^+ e^+ e^-μ+→e+e+e− decay. The experimental apparatus, a light-weight tracker based on custom High-Voltage Monolithic Active Pixel Sensors placed in a 1 T magnetic field is currently under construction at the Paul Scherrer Institute, where it will fully use the intense 10^88\mu^+μ+/s beam available. A final sensitivity of 1 \cdot 10^{-16}1⋅10−16 is envisioned for a phase II experiment, driving the development of a new high-intensity continuous muon source which will deliver >10^99\mu^+μ+/s to the experiment.
Electron-positron annihilation into three pions and the radiative return
2005
The Monte Carlo event generator PHOKHARA, which simulates hadron and muon production at electron-positron colliders through radiative return, has been extended to final states with three pions. A model for the form factor based on generalized vector dominance has been employed, which is consistent with presently available experimental observations.
The radiative return at phi- and B-factories: FSR for muon pair production at next-to-leading order
2004
Muon pair production through the radiative return is of importance for a measurement of the hadronic production cross section in two ways: it provides an independent calibration and it may give rise to an important background for a measurement of the pion form factor. With this motivation the Monte Carlo event generator PHOKHARA is extended to include next-to-leading order radiative corrections to the reaction $e^+e^-\to \mu^+\mu^-\gamma$. Furthermore, virtual ISR corrections to FSR from pions are introduced, which extends the applicability of the generator into a new kinematical regime. Finally, the effect of photon vacuum polarization is introduced into this new version of the generator.
Exclusive final state hadron observables from neutrino-nucleus multi-nucleon knockout
2020
We present results of an updated calculation of the 2p2h (two particle two hole) contribution to the neutrino-induced charge-current cross section. We provide also some exclusive observables, interesting from the point of view of experimental studies, e.g. distributions of momenta of the outgoing nucleons and of available energy, which we compare with the results obtained within the NEUT generator. We also compute, and separate from the total, the contributions of 3p3h mechanisms. Finally, we discuss the differences between the present results and previous implementations of the model in MC event-generators, done at the level of inclusive cross sections, which might significantly influence …
ALICE: Physics performance report, volume II
2006
ALICE is a general-purpose heavy-ion experiment designed to study the physics of strongly interacting matter and the quark-gluon plasma in nucleus-nucleus collisions at the LHC. It currently involves more than 900 physicists and senior engineers, from both the nuclear and high-energy physics sectors, from over 90 institutions in about 30 countries. The ALICE detector is designed to cope with the highest particle multiplicities above those anticipated for Pb-Pb collisions (dN(ch)/dy up to 8000) and it will be operational at the start-up of the LHC. In addition to heavy systems, the ALICE Collaboration will study collisions of lower-mass ions, which are a means of varying the energy density, …
Measurement of the effective Bs0→K+K− lifetime
2012
A precise determination of the effective $B_s^0 \rightarrow K^+ K^-$ lifetime can be used to constrain contributions from physics beyond the Standard Model in the $B_s^0$ meson system. Conventional approaches select $B$ meson decay products that are significantly displaced from the $B$ meson production vertex. As a consequence, $B$ mesons with low decay times are suppressed, introducing a bias to the decay time spectrum which must be corrected. This analysis uses a technique that explicitly avoids a lifetime bias by using a neural network based trigger and event selection. Using 1.0 fb$^{-1}$ of data recorded by the LHCb experiment, the effective $B_s^0 \rightarrow K^+ K^-$ lifetime is meas…
Inclusive production of the η and ω mesons in Z decays, and the muonic branching ratio of the ω
2002
AbstractThe inclusive production of the η and ω(782) mesons is measured in the π+π−π0 decay mode in hadronic Z decays and compared to model predictions. The analysis is based on 4 million hadronic Z decays recorded by the ALEPH detector between 1991 and 1995. The η production rate for xp=pmeson/pbeam>0.10 is found to be 0.355±0.011stat±0.024sys per event, and the ω production rate for xp>0.05 is measured as 0.585±0.019stat±0.033sys per event. The branching ratio for ω→μ+μ− is investigated. A total of 18.1±5.9 events are observed, from which the muonic branching ratio is measured for the first time to be BR(ω→μ+μ−)=(9.0±2.9stat±1.1sys)×10−5.
Nucleon form factors, B-meson factories and the radiative return
2004
The feasibility of a measurement of the electric and magnetic nucleon form factors at $B$-meson factories through the radiative return is studied. Angular distributions allow a separation of the contributions from the two form factors. The distributions are presented for the laboratory and the hadronic rest frame, and the advantages of different coordinate systems are investigated. It is demonstrated that $Q^2$ values up to 8 or even 9 GeV$^2$ are within reach. The Monte Carlo event generator PHOKHARA is extended to nucleon final states, and results are presented which include Next-to-Leading Order radiative corrections from initial-state radiation. The impact of angular cuts on rates and d…