1728923
Performance of the LHCb muon system
The performance of the LHCb Muon system and its stability across the full 2010 data taking with LHC running at root s = 7 TeV energy is studied. The optimization of the detector setting and the time calibration performed with the first collisions delivered by LHC is described. Particle rates, measured for the wide range of luminosities and beam operation conditions experienced during the run, are compared with the values expected from simulation. The space and time alignment of the detectors, chamber efficiency, time resolution and cluster size are evaluated. The detector performance is found to be as expected from specifications or better. Notably the overall efficiency is well above the design requirements.
122048635
Time resolution limits of the MWPCs for the LHCb muon system
Abstract Detailed simulations of the timing properties of the Multi-Wire-Proportional-Chambers of the LHCb muon system are compared with actual measurements. The simulated time resolution is in good agreement with the measurement which allows to study the resolution limiting parameters like diffusion, charge deposit fluctuations, cluster position fluctuations, electronics noise, track position and wire spacing to show how they affect the performance of the system. Methods to improve the time resolution of the muon chambers are discussed.
18491403
Study of beauty hadron decays into pairs of charm hadrons
First observations of the decays Λb 0 → Λc +D(s) - are reported using data corresponding to an integrated luminosity of 3fb-1 collected at 7 and 8 TeV center-of-mass energies in proton-proton collisions with the LHCb detector. In addition, the most precise measurement of the branching fraction B(Bs 0→D+Ds -) is made and a search is performed for the decays B(s) 0→Λc +Λc -. The results obtained are B(Λb 0→Λc +D-)/ B(Λb 0→Λc +D s -)=0.042±0.003(stat)±0.003(syst), [B(Λb 0→Λc +D s -)/B(B0→D+D s -)]/[B(Λb 0→Λ c +π-)/B(B0→D +π-)]=0.96±0.02(stat)±0.06(syst),B(B s 0→D+Ds -)/ B(B0→D+Ds -)=0. 038±0.004(stat)±0.003(syst),B(B0→Λ c +Λc -)/B(B 0→D+Ds -)<0.0022[95%C.L.], B(Bs 0→Λc +Λ c -)/B(Bs 0→D+D s -)<0.30[95%C.L.]. Measurement of the mass of the Λb 0 baryon relative to the B0 meson gives M(Λb 0)-M(B0)=339. 72±0.24(stat)±0.18(syst)MeV/c2. This result provides the most precise measurement of the mass of the Λb 0 baryon to date.
119113679
Search for CP violation in the decay $D^+ \to \pi^-\pi^+\pi^+$
A search for CP violation in the phase space of the decay $D^+\to\pi^-\pi^+\pi^+$ is reported using $pp$ collision data, corresponding to an integrated luminosity of 1.0 fb$^{-1}$, collected by the LHCb experiment at a centre-of-mass energy of 7 TeV. The Dalitz plot distributions for $3.1\times 10^6$ $D^+$ and $D^-$ candidates are compared with binned and unbinned model-independent techniques. No evidence for CP violation is found.
122081812
Study of $\eta-\eta^{\prime}$ mixing from measurement of $B^0_{(s)} \rightarrow J/\psi \eta^{(\prime)}$ decay rates
A study of $B^0$~and $B^0_s$ meson decays into $J/\psi\eta$~and $J/\psi\eta^{\prime}$ final states is performed using a data set of proton-proton collisions at centre-of-mass energies of 7 and 8TeV, collected by the LHCb experiment and corresponding to 3.0fb$^{-1}$ of integrated luminosity. The decay $B^0 \rightarrow J/\psi \eta^{\prime}$ is observed for thefirst time. The following ratios of branching fractions are measured: $$ \frac{\mathcal{B}(B^0 \rightarrow J/\psi \eta^{\prime})}{\mathcal{B}(B^0_s \rightarrow J/\psi \eta^{\prime})} = (2.28\pm0.65\,(stat)\,\pm0.10\,(syst)\,\pm0.13\,(f_{s}/f_{d}))\times10^{-2},$$ $$ \frac{\mathcal{B}(B^0 \rightarrow J/\psi \eta)}{\mathcal{B}(B^0_s \rightarrow J/\psi \eta)} = (1.85\pm0.61\,(stat)\,\pm0.09\,(syst)\,\pm0.11\,(f_{s}/f_{d}))\times10^{-2},$$ where the third uncertainty is related to the present knowledge of $f_{s}/f_{d}$, the ratio between the probabilities for a $b$ quark to form a $B^0_s$ or $B^0$ meson. The branching fraction ratios are used to determine the parameters of $\eta-\eta^{\prime}$ meson mixing. In addition, the first evidence for the decay $B^0_s \rightarrow \psi(2S) \eta^{\prime}$ is reported, and the relative branching fraction is measured, 
$$\frac{\mathcal{B}(B^0_s \rightarrow \psi(2S) \eta^{\prime})}{\mathcal{B}(B^0_s \rightarrow J/\psi \eta^{\prime})} = (38.7\pm9.0\,(stat)\,\pm1.3\,(syst)\,\pm0.9(\mathcal{B}))\times10^{-2},$$ 
where the third uncertainty is due to the limited knowledge of the branching fractions of $J/\psi$ and $\psi(2S)$~mesons.
119287240
Searches for Majorana neutrinos in $B^-$ decays
Searches for heavy Majorana neutrinos in B- decays in final states containing hadrons plus a \mu- \mu- pair have been performed using 0.41/fb of data collected with the LHCb detector in proton-proton collisions at a center-of-mass energy of 7 TeV. The D+ \mu- \mu- and D*+ \mu- \mu- final states can arise from the presence of virtual Majorana neutrinos of any mass. Other final states containing \pi+, Ds+, or D0\pi+ can be mediated by an on-shell Majorana neutrino. No signals are found and upper limits are set on Majorana neutrino production as a function of mass, and also on the B- decay branching fractions.
2051750
The H i gas content of galaxies around Abell 370, a galaxy cluster at z= 0.37
This research was supported under Australian Research Council’s 
Discovery Projects funding scheme (project no. 0559688).
55602552
SINGLE-SHOT LONGITUDINAL DIAGNOSTICS WITH THZ RADIATION AT THE FREE-ELECTRON LASER FLASH
The longitudinal charge distribution in the electron bunches has a strong impact on the lasing process in a Free-Electron Laser based on the principle of Self Amplified Spontaneous Emission of radiation. For the ultraviolet and soft X ray FEL FLASH at DESY, structures in the range of ten to hundred micrometers play a crucial role. The investigation of the longitudinal charge distribution in the electron bunches on a bunch-by-bunch basis is an important issue for optimizing the bunch compression and improving the performance of the machine. This paper introduces a new tool for longitudinal diagnostics based on THz spectroscopy of coherent radiation. A novel spectrometer has been designed which permits to analyze the radiation of single electron bunches in a broad spectral range and with high resolution. Preliminary measurements with this spectrometer are presented.
28627243
SINGLE SHOT LONGITUDINAL BUNCH PROFILE MEASUREMENTS AT FLASH USING ELECTRO-OPTIC TECHNIQUES
For the high-gain operation of a SASE FEL, extremely short electron bunches are essential to generate sufficiently high peak currents. At the superconducting linac of FLASH at DESY, we have installed an electro-optic experiment with temporal decoding and spectral decoding to probe the time structure of the electric field of single sub-200 fs electron bunches. In this technique, the fieldinduced birefringence in an electro-optic crystal is encoded on a chirped ps laser pulse. The longitudinal electric field profile of the electron bunch is then obtained from the encoded optical pulse by a single-shot cross correlation with a 30 fs laser pulse using a second-harmonic crystal (temporal decoding) or by a single-shot measurement of its spectrum (spectral decoding). In the temporal decoding measurements an electro-optic signal of 110 fs FWHM was observed, which is limited by the material properties of the particular electro-optic crystal used. Bunch profile and time jitter measurements were obtained simultaneously with SASE operation.
120738580
Performance of the multianode cylindrical silicon drift detector in the CERES NA45 experiment: first results☆
Abstract A silicon drift detector of circular geometry giving unambiguously the radial and azimuthal coordinates of particle's interaction point for events with high multiplicity is part of the experimental set up of the NA45 experiment at CERN SPS. The paper reviews the characteristics of the detector and of its assembly among the other detectors of the experiment. The first experimental results showing the performance of the detector in term of resolution and its effectiveness in reconstructing the position of the event are reported.
49382390
MEASUREMENT AND STABILIZATION OF THE BUNCH ARRIVAL TIME AT FLASH
To fully exploit the experimental opportunities offered by the 10 − 30 fs long light pulses from FLASH, e.g. in pump-probe experiments, precise measurements and control of the electron-bunch arrival-time on the 10 fs scale are needed. A bunch arrival time monitor which uses the optical synchronization system of FLASH as a reference has been developed for this purpose. The bunch-induced signal from a GHz-bandwidth beam pick-up is guided into an electro-optical modulator in which the periodic laser pulse train of the optical synchronization system experiences an amplitude modulation. Detection of this modulation allows to determine the bunch arrival time with a resolution of better than 10 fs. The superconducting linac of FLASH generates trains of up to 800 bunches. The signals from the bunch arrival time monitor can be used for an intrabunch train feedback stabilizing the arrival time to 40 fs (rms). The feedback is capable of generating well-defined arrival time patterns within a bunch train which are useful for overlap-scans in pump-probe experiments. First results from the feedback installed at FLASH will be presented.