2,685 research outputs found
Physics Opportunities with the FCC-hh Injectors
In this chapter we explore a few examples of physics opportunities using the
existing chain of accelerators at CERN, including potential upgrades. In this
context the LHC ring is also considered as a part of the injector system. The
objective is to find examples that constitute sensitive probes of New Physics
that ideally cannot be done elsewhere or can be done significantly better at
theCERN accelerator complex. Some of these physics opportunities may require a
more flexible injector complex with additional functionality than that just
needed to inject protons into the FCC-hh at the right energy, intensity and
bunch structure. Therefore it is timely to discuss these options concurrently
with the conceptual design of the FCC-hh injector system.Comment: 13 pages, chapter 5 in Physics at the FCC-hh, a 100 TeV pp collide
Angular analysis of the decay in the low- region
An angular analysis of the decay is performed using a data sample, corresponding to an integrated luminosity of 3.0 {\mbox{fb}^{-1}}, collected by the LHCb experiment in collisions at centre-of-mass energies of 7 and 8 TeV during 2011 and 2012. For the first time several observables are measured in the dielectron mass squared () interval between 0.002 and 1.120. The angular observables and which are related to the polarisation and to the lepton forward-backward asymmetry, are measured to be and , where the first uncertainty is statistical and the second systematic. The angular observables and which are sensitive to the photon polarisation in this range, are found to be and . The results are
consistent with Standard Model predictions
Measurement of asymmetries and polarisation fractions in decays
An angular analysis of the decay is performed using collisions corresponding to an integrated luminosity of collected by the LHCb experiment at a centre-of-mass energy TeV. A combined angular and mass analysis separates six helicity amplitudes and allows the measurement of the longitudinal polarisation fraction for the decay. A large scalar contribution from the and resonances is found, allowing the determination of additional asymmetries. Triple product and direct asymmetries are determined to be compatible with the Standard Model expectations. The branching fraction is measured to be
Luminometer for the future International Linear Collider - simulation and beam test results
LumiCal will be the luminosity calorimeter for the proposed International
Large Detector of the International Linear Collider (ILC). The ILC physics
program requires the integrated luminosity to be measured with a relative
precision on the order of 10e-3, or 10e-4 when running in GigaZ mode.
Luminosity will be determined by counting Bhabha scattering events coincident
in the two calorimeter modules placed symmetrically on opposite sides of the
interaction point. To meet these goals, the energy resolution of the
calorimeter must be better than 1.5% at high energies. LumiCal has been
designed as a 30-layer sampling calorimeter with tungsten as the passive
material and silicon as the active material. Monte Carlo simulation using the
Geant4 software framework has been used to identify design elements which
adversely impact energy resolution and correct for them without loss of
statistics. BeamCal, covering polar angles smaller than LumiCal, will serve for
beam tuning, luminosity optimisation and high energy electron detection.
Secondly, prototypes of the sensors and electronics for both detectors have
been evaluated during beam tests, the results of which are also presented here.Comment: Technology and Instrumentation in Particle Physics 2011, Chicago, IL,
USA. Presented June 11, 2011, and submitted to Physics Procedi
Measurement of ISR-FSR interference in the processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi- gamma
Charge asymmetry in processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi-
gamma is measured using 232 fb-1 of data collected with the BABAR detector at
center-of-mass energies near 10.58 GeV. An observable is introduced and shown
to be very robust against detector asymmetries while keeping a large
sensitivity to the physical charge asymmetry that results from the interference
between initial and final state radiation. The asymmetry is determined as
afunction of the invariant mass of the final-state tracks from production
threshold to a few GeV/c2. It is compared to the expectation from QED for e+ e-
--> mu+ mu- gamma and from theoretical models for e+ e- --> pi+ pi- gamma. A
clear interference pattern is observed in e+ e- --> pi+ pi- gamma, particularly
in the vicinity of the f_2(1270) resonance. The inferred rate of lowest order
FSR production is consistent with the QED expectation for e+ e- --> mu+ mu-
gamma, and is negligibly small for e+ e- --> pi+ pi- gamma.Comment: 32 pages,29 figures, to be submitted to Phys. Rev.
Observation of the decay from an amplitude analysis of decays
Proton-proton collision data recorded in 2011 and 2012 by the LHCb experiment, corresponding to an integrated luminosity of 3.0\invfb, are analysed to search for the charmless decay. More than 600 signal decays are selected and used to perform an amplitude analysis from which the decay is observed for the first time with 7.1 standard deviations significance. The fraction of decays yielding a longitudinally polarised final state is measured to be . The branching fraction, using the decay as reference, is also reported as
Observation of two new baryon resonances
Two structures are observed close to the kinematic threshold in the mass spectrum in a sample of proton-proton collision data, corresponding
to an integrated luminosity of 3.0 fb recorded by the LHCb experiment.
In the quark model, two baryonic resonances with quark content are
expected in this mass region: the spin-parity and
states, denoted and .
Interpreting the structures as these resonances, we measure the mass
differences and the width of the heavier state to be
MeV,
MeV,
MeV, where the first and second
uncertainties are statistical and systematic, respectively. The width of the
lighter state is consistent with zero, and we place an upper limit of
MeV at 95% confidence level. Relative
production rates of these states are also reported.Comment: 17 pages, 2 figure
Observation of an Excited Bc+ State
Using pp collision data corresponding to an integrated luminosity of 8.5 fb-1 recorded by the LHCb experiment at center-of-mass energies of s=7, 8, and 13 TeV, the observation of an excited Bc+ state in the Bc+π+π- invariant-mass spectrum is reported. The observed peak has a mass of 6841.2±0.6(stat)±0.1(syst)±0.8(Bc+) MeV/c2, where the last uncertainty is due to the limited knowledge of the Bc+ mass. It is consistent with expectations of the Bc∗(2S31)+ state reconstructed without the low-energy photon from the Bc∗(1S31)+→Bc+γ decay following Bc∗(2S31)+→Bc∗(1S31)+π+π-. A second state is seen with a global (local) statistical significance of 2.2σ (3.2σ) and a mass of 6872.1±1.3(stat)±0.1(syst)±0.8(Bc+) MeV/c2, and is consistent with the Bc(2S10)+ state. These mass measurements are the most precise to date
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