Noncommutative waves have infinite propagation speed

We prove the existence of global solutions to the Cauchy problem for noncommutative nonlinear wave equations in arbitrary even spatial dimensions where the noncommutativity is only in the spatial directions. We find that for existence there are no conditions on the degree of the nonlinearity provided the potential is positive. We furthermore prove that nonlinear noncommutative waves have infinite propagation speed, i.e., if the initial conditions at time 0 have a compact support then for any positive time the support of the solution can be arbitrarily large.Comment: 15 pages, references adde

Spin alignment and violation of the OZI rule in exclusive ω\omega and ϕ\phi production in pp collisions

Exclusive production of the isoscalar vector mesons $\omega$ and $\phi$ is measured with a 190 GeV$/c$ proton beam impinging on a liquid hydrogen target. Cross section ratios are determined in three intervals of the Feynman variable $x_{F}$ of the fast proton. A significant violation of the OZI rule is found, confirming earlier findings. Its kinematic dependence on $x_{F}$ and on the invariant mass $M_{p\mathrm{V}}$ of the system formed by fast proton $p_\mathrm{fast}$ and vector meson $V$ is discussed in terms of diffractive production of $p_\mathrm{fast}V$ resonances in competition with central production. The measurement of the spin density matrix element $\rho_{00}$ of the vector mesons in different selected reference frames provides another handle to distinguish the contributions of these two major reaction types. Again, dependences of the alignment on $x_{F}$ and on $M_{p\mathrm{V}}$ are found. Most of the observations can be traced back to the existence of several excited baryon states contributing to $\omega$ production which are absent in the case of the $\phi$ meson. Removing the low-mass $M_{p\mathrm{V}}$ resonant region, the OZI rule is found to be violated by a factor of eight, independently of $x_\mathrm{F}$.Comment: 23 pages, 13 figures and 5 table

Cohesion as ‘common sense’: Everyday narratives of community and cohesion in New Labour’s Britain

The final, definitive version of this paper has been published in Politics, Vol. 36(3) July 2016, DOI: 10.1177/0263395715620811 published by SAGE Publishing. All rights reservedThis article engages with popular narratives of community and cohesion, explored through a series of focus groups in Bradford and Birmingham. This article argues that the participants interviewed used discourses propagated by government to make sense of these narratives in their neighbourhoods and communities. The use of these discourses constructs what Gramsci calls a ‘common sense’ position, which legitimises a specific and targeted notion of cohesion. However, participants can contaminate these discourses, which can lead to subtle changes or explicit challenges to dominant discourses on community and cohesion in the United Kingdom.Peer reviewe

Collins and Sivers asymmetries in muonproduction of pions and kaons off transversely polarised proton

Measurements of the Collins and Sivers asymmetries for charged pions and charged and neutral kaons produced in semi-inclusive deep-inelastic scattering of high energy muons off transversely polarised protons are presented. The results were obtained using all the available COMPASS proton data, which were taken in the years 2007 and 2010. The Collins asymmetries exhibit in the valence region a non-zero signal for pions and there are hints of non-zero signal also for kaons. The Sivers asymmetries are found to be positive for positive pions and kaons and compatible with zero otherwise.Comment: 15 pages, 13 figures and 1 tabl

Measurement of the charged-pion polarisability

The COMPASS collaboration at CERN has investigated pion Compton scattering, $\pi^-\gamma\rightarrow \pi^-\gamma$, at centre-of-mass energy below 3.5 pion masses. The process is embedded in the reaction $\pi^-\mathrm{Ni}\rightarrow\pi^-\gamma\;\mathrm{Ni}$, which is initiated by 190\,GeV pions impinging on a nickel target. The exchange of quasi-real photons is selected by isolating the sharp Coulomb peak observed at smallest momentum transfers, $Q^2<0.0015$\,(GeV/$c$)$^2$. From a sample of 63\,000 events the pion electric polarisability is determined to be $\alpha_\pi\ =\ (\,2.0\ \pm\ 0.6_{\mbox{\scriptsize stat}}\ \pm\ 0.7_{\mbox{\scriptsize syst}}\,) \times 10^{-4}\,\mbox{fm}^3$under the assumption$\alpha_\pi=-\beta_\pi$, which relates the electric and magnetic dipole polarisabilities. It is the most precise measurement of this fundamental low-energy parameter of strong interaction, that has been addressed since long by various methods with conflicting outcomes. While this result is in tension with previous dedicated measurements, it is found in agreement with the expectation from chiral perturbation theory. An additional measurement replacing pions by muons, for which the cross-section behavior is unambigiously known, was performed for an independent estimate of the systematic uncertainty.Comment: Published version: 9 pages, 3 figures, 1 tabl

Search for exclusive photoproduction of Zc±_c^{\pm}(3900) at COMPASS

A search for the exclusive production of the $Z_c^{\pm}(3900)$ hadron by virtual photons has been performed in the channel $Z_c^{\pm}(3900)\rightarrow J/\psi \pi^{\pm}$. The data cover the range from 7 GeV to 19 GeV in the centre-of-mass energy of the photon-nucleon system. The full set of the COMPASS data set collected with a muon beam between 2002 and 2011 has been used. An upper limit for the ratio $BR(Z_c^{\pm}(3900)\rightarrow J/\psi \pi^{\pm} )\times \sigma_{ \gamma~N \rightarrow Z_c^{\pm}(3900)~ N} /\sigma_{\gamma~N \rightarrow J/\psi~ N}$ of $3.7\times10^{-3}$ has been established at the confidence level of 90%.Comment: 8 pages, 3 figures, 1 tabl

Spin alignment and violation of the OZI rule in exclusive ω and ϕ production in pp collisions

Exclusive production of the isoscalar vector mesons omega and phi is measured with a 190 GeV/c proton beam impinging on a liquid hydrogen target. Cross section ratios are determined in three intervals of the Feynman variable x(F) of the fast proton. A significant violation of the OZI rule is found, confirming earlier findings. Its kinematic dependence on xF and on the invariant mass M-pV of the system formed by fast proton p(fast) and vector meson V is discussed in terms of diffractive production of p(fast) V resonances in competition with central production. The measurement of the spin density matrix element rho(00) of the vector mesons in different selected reference frames provides another handle to distinguish the contributions of these two major reaction types. Again, dependences of the alignment on x(F) and on M-pV are found. Most of the observations can be traced back to the existence of several excited baryon states contributing to omega production which are absent in the case of the phi meson. Removing the low-mass M-pV resonant region, the OZI rule is found to be violated by a factor of eight, independently of x(F)

Spin alignment and violation of the OZI rule in exclusive ω and ϕ production in pp collisions

Exclusive production of the isoscalar vector mesons omega and phi is measured with a 190 GeV/c proton beam impinging on a liquid hydrogen target. Cross section ratios are determined in three intervals of the Feynman variable x(F) of the fast proton. A significant violation of the OZI rule is found, confirming earlier findings. Its kinematic dependence on xF and on the invariant mass M-pV of the system formed by fast proton p(fast) and vector meson V is discussed in terms of diffractive production of p(fast) V resonances in competition with central production. The measurement of the spin density matrix element rho(00) of the vector mesons in different selected reference frames provides another handle to distinguish the contributions of these two major reaction types. Again, dependences of the alignment on x(F) and on M-pV are found. Most of the observations can be traced back to the existence of several excited baryon states contributing to omega production which are absent in the case of the phi meson. Removing the low-mass M-pV resonant region, the OZI rule is found to be violated by a factor of eight, independently of x(F)

Measurement of azimuthal hadron asymmetries in semi-inclusive deep inelastic scattering off unpolarised nucleons

Spin-averaged asymmetries in the azimuthal distributions of positive and negative hadrons produced in deep inelastic scattering were measured using the CERN SPS longitudinally polarised muon beam at 160 GeV/c and a (LiD)-Li-6 target. The amplitudes of the three azimuthal modulations cos phi(h), cos 2 phi(h) and sin phi(h) were obtained binning the data separately in each of the relevant kinematic variables x, z or p(T)(h), and binning in a three-dimensional grid of these three variables. The amplitudes of the cos phi(h) and cos 2 phi(h) modulations show strong kinematic dependencies both for positive and negative hadrons