A triple GEM detector with two dimensional readout

The triple GEM detector is a micropattern gas detector which consists of a primary ionisation gap and three consecutive gas electron multiplier (GEM) foils. A printed circuit board with readout strips detects the current induced by the drifting electron cloud originating from the last GEM stage. Thus the gas amplification and the signal readout are completely separated. Triple GEM detectors are being developed as a possible technology for the inner tracking in the LHCb experiment. In an earlier note we have reported first experience with such a detector in a test beam at PSI. Here we describe the construction of an improved version (thinner transfer gaps, segmented GEM foils, two dimensional readout). Results from performance measurements are presented using intense hadronic beams as well as cosmic ray data.Comment: 20 pages, 24 figure

A stacking method to study the gamma-ray emission of source samples based on the co-adding of Fermi LAT count maps

We present a stacking method that makes use of co-added maps of gamma-ray counts produced from data taken with the Fermi Large Area Telescope. Sources with low integrated gamma-ray fluxes that are not detected individually may become detectable when their corresponding count maps are added. The combined data set is analyzed with a maximum likelihood method taking into account the contribution from point-like and diffuse background sources. For both simulated and real data, detection significance and integrated gamma-ray flux are investigated for different numbers of stacked sources using the public Fermi Science Tools for analysis and data preparation. The co-adding is done such that potential source signals add constructively, in contrast to the signals from background sources, which allows the stacked data to be described with simply structured models. We show, for different scenarios, that the stacking method can be used to increase the cumulative significance of a sample of sources and to characterize the corresponding gamma-ray emission. The method can, for instance, help to search for gamma-ray emission from galaxy clusters.Comment: accepted for publication in Astronomy & Astrophysics, 10 pages, 12 figure

Reflections on a Measurement of the Gravitational Constant Using a Beam Balance and 13 Tons of Mercury

In 2006, a final result of a measurement of the gravitational constant $G$ performed by researchers at the University of Z\"urich was published. A value of G=6.674\,252(122)\times 10^{-11}\,\mbox{m}^3\,\mbox{kg}^{-1}\,\mbox{s}^{-2} was obtained after an experimental effort that lasted over one decade. Here, we briefly summarize the measurement and discuss the strengths and weaknesses of this approach.Comment: 13 pages, 5 figures accepted for publication in Phil. Trans. R. Soc.

Vestibular and auditory deficits in Fabry disease and their response to enzyme replacement therapy

Progressive hearing (pHL) and vestibular (pVL) loss are frequent deficits in Fabry disease (FD). Recently, enzyme replacement therapy (ERT) with human α-galactosidase A has become available. Here, we investigate the association between pHL and pVL in FD and their ERT responses. Pure tone audiometry (PTA) and head impulse testing (HIT) were administered at baseline in 47 patients (25 male, 18-0 y; 22 female, 17-4 y), of whom 24 also received caloric irrigation (CI). Of the 47 patients, 38 (24 male) were tested both before and during ERT (follow- up ≤60 months). ERT consisted of agalsidase alfa infusions. At baseline, pHL was present in 88% of males and 86% of females. Over all tested frequencies (range: 0.5- kHz), pHL was significantly (two-way ANOVA: p 0.05). We conclude that pHL and pVL prevalences are similar in FD. To detect pVL, HIT is more sensitive than CI. We speculate that pHL and pVL emerge from lesions within the vestibulocochlear labyrinth, because no specific patterns of vestibulo-cochlear deficits were observed, as expected if lesions were more proximal along the inferior or superior branch of the vestibulo-cochlear nerve or labyrinthine artery. Finally, ERT stabilizes auditory and even improves vestibular functio

Weak-field limit of Kaluza-Klein models with spherical compactification: experimental constraints

We investigate the classical gravitational tests for the six-dimensional Kaluza-Klein model with spherical (of a radius $a$) compactification of the internal space. The model contains also a bare multidimensional cosmological constant $\Lambda_6$. The matter, which corresponds to this ansatz, can be simulated by a perfect fluid with the vacuum equation of state in the external space and an arbitrary equation of state with the parameter $\omega_1$ in the internal space. For example, $\omega_1=1$ and $\omega_1=2$ correspond to the monopole two-forms and the Casimir effect, respectively. In the particular case $\Lambda_6=0$, the parameter $\omega_1$ is also absent: $\omega_1=0$. In the weak-field approximation, we perturb the background ansatz by a point-like mass. We demonstrate that in the case $\omega_1>0$ the perturbed metric coefficients have the Yukawa type corrections with respect to the usual Newtonian gravitational potential. The inverse square law experiments restrict the parameters of the model: $a/\sqrt{\omega_1}\lesssim 6\times10^{-3}\ {{cm}}$. Therefore, in the Solar system the parameterized post-Newtonian parameter$\gamma$is equal to 1 with very high accuracy. Thus, our model satisfies the gravitational experiments (the deflection of light and the time delay of radar echoes) at the same level of accuracy as General Relativity. We demonstrate also that our background matter provides the stable compactification of the internal space in the case$\omega_1>0$. However, if$\omega_1=0$, then the parameterized post-Newtonian parameter$\gamma=1/3$, which strongly contradicts the observations.Comment: 8 pages, no figures, revised version, equations and references added, accepted for publication in Phys. Rev. D. arXiv admin note: significant text overlap with arXiv:1107.338

Measurement of CPCP violation parameters in B0→DK∗0{B}^{0}\rightarrow{}D{K}^{*0} decays

An analysis of ${B}^{0}\rightarrow{}D{K}^{*0}$ decays is presented, where $D$ represents an admixture of ${D}^{0}$ and ${\overline{D}}^{0}$ mesons reconstructed in four separate final states: ${K}^{-{}}{\pi{}}^{+}$, ${\pi{}}^{-{}}{K}^{+}$, ${K}^{+}{K}^{-{}}$ and ${\pi{}}^{+}{\pi{}}^{-{}}$. The data sample corresponds to $3.0\text{ }\text{ }{\mathrm{fb}}^{-{}1}$ of proton-proton collision, collected by the LHCb experiment. Measurements of several observables are performed, including $CP$ asymmetries. The most precise determination is presented of ${r}_{B}(D{K}^{*0})$, the magnitude of the ratio of the amplitudes of the decay ${B}^{0}\rightarrow{}D{K}^{+}{\pi{}}^{-{}}$ with a $b\rightarrow{}u$ or a $b\rightarrow{}c$ transition, in a $K\pi{}$ mass region of $\pm50 \text{ }\mathrm{MeV}/{c}^{2}$ around the ${K}^{*}(892)$ mass and for an absolute value of the cosine of the ${K}^{*0}$ helicity angle larger than 0.4

First observation of the decay B+c→J/ψK+

The decay B+c→J/ψK+ is observed for the first time using a data sample, corresponding to an integrated luminosity of 1.0 fb−1, collected by the LHCb experiment in pp collisions at a centre-of-mass energy of 7 TeV. A yield of 46 ± 12 events is reported, with a significance of 5.0 standard deviations. The ratio of the branching fraction of B+c→J/ψK+ to that of B+c→J/ψπ+ is measured to be 0.069 ± 0.019 ± 0.005, where the first uncertainty is statistical and the second is systematic

First observation of the decay B∗s2(5840)0→B∗+K− and studies of excited Bs mesons

The properties of the orbitally excited (L=1) B0s states are studied by using 1.0  fb−1 of pp collisions at s√=7  TeV collected with the LHCb detector. The first observation of the B∗s2(5840)0 meson decaying to B*+K− is reported, and the corresponding branching fraction measured relative to the B+K− decay mode. The Bs1(5830)0→B*+K− decay is observed as well. The width of the B∗s2(5840)0 state is measured for the first time, and the masses of the two states are determined with the highest precision to date. The observation of the B∗s2(5840)0→B*+K− decay favors the spin-parity assignment JP=2+ for the B∗s2(5840)0 meson. In addition, the most precise measurement of the mass difference m(B*+)−m(B+)=45.01±0.30(stat)±0.23(syst)  MeV/c2 is obtained

Search for CP violation in the decay D+→π−π+π+

A search for CP violation in the phase space of the decay D+→π−π+π+D+→π−π+π+ 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 3.1×1063.1×106D+D+ and D−D− candidates are compared with binned and unbinned model-independent techniques. No evidence for CP violation is found