Measurement of the charged-pion polarisability at COMPASS

The electric (${\alpha}_{\pi}$) and the magnetic (${\beta}_{\pi}$) polarisabilities are fundamental properties of the pion characterising the rigidity of its internal structure. They have been precisely measured at the COMPASS experiment at CERN with a ${\pi}^{-}$ beam of 190~GeV/c assuming ${\alpha}_{\pi}+{\beta}_{\pi}=0$. Muons of the same momentum were used for controlling of systematic effects. The obtained result ${\alpha}_{\pi}=-{\beta}_{\pi}=(2.0\pm 0.6_{stat.}\pm 0.7_{syst.})\times 10^{-4} fm^3$ is in agreement with the prediction of the Chiral Perturbation Theory.Comment: EPS-HEP-2015 proceeding

Search for muoproduction of the X(3872) at COMPASS

Exotic charmonium-like states have been observed by various experiments over the last 15 years, but their nature is still under discussion. Photo-(muo)production is a new promising instrument to study them. COMPASS, a fixed target experiment at CERN, analyzed the full set of the data collected with a muon beam between 2002 and 2011, covering the range from 7 GeV to 19 GeV in the centre-of-mass energy of the virtual photon-nucleon system. A signal in the mass spectrum of $J/\psi\pi^+\pi^-$ with the statistical significance of 4.1 $\sigma$ was observed in the reaction $\mu^+~N \rightarrow \mu^+(J/\psi\pi^+\pi^- )\pi^{\pm} N'$. Its mass and width are consistent with those of the $X(3872)$. The shape of the $\pi^+\pi^-$ mass distribution from the observed decay into $J/\psi\pi^+\pi^-$ is different from previous observations for $X(3872)$. The observed signal may be interpreted as possible evidence of a new charmonium state $\widetilde{X}(3872)$. It could be associated with a neutral partner of $X(3872)$ with $C = -1$ predicted by a tetraquark model.Comment: After the talk at the BEACH18 conference. arXiv admin note: text overlap with arXiv:1712.0134

Charmed hadron photoproduction at COMPASS

Photoproduction of the charmonium-like state $Z_{c}(4200)$ and the charmed baryon $\Lambda_{c}^{\ast }(2940)$ is investigated with an effective Lagrangian approach and the Regge trajectories applying to the COMPASS experiment. Combining the experimental data from COMPASS and our theoretical model we estimate the upper limit of $\Gamma_{Z_{c}(4200)\rightarrow J/\psi \pi }$ to be of about 37 MeV. Moreover, the possibility to produce $\Lambda_{c}^{\ast }(2940)$ at COMPASS is discussed. It seems one can try to search for this hadron in the missing mass spectrum since the $t$-channel is dominating for the $\Lambda_{c}^{\ast }(2940)$ photoproduction.Comment: Proceedings of the Second International Symposium on Physics of Photons (ISPP 15), Lanzhou, China, July 201

Mjerenje pionske polarizivosti na COMPASS-U

The electromagnetic structure of pions is probed in π − + (A, Z) → π − + (A, Z) + γ Compton scattering in inverse kinematics (Primakoff reaction) and described by the electric (απ) and the magnetic (βπ) polarizabilities that depend on the rigidity of pion’s internal structure as a composite particle. Values for pion polarizabilities can be extracted from the comparison of the differential cross section for scattering of pointlike pions with the measured cross section. The pion polarizability measurement was performed with a π − beam of 190 GeV. The high beam intensity, the good spectrometer resolution, the high rate capability, the high acceptance and the possibility to use pion and muon beams, unique to the COMPASS experiment, provide the tools to measure precisely the pion polarizabilities in the Primakoff reaction. The preliminary result for pion polarizabilities under the assumption of απ + βπ = 0 is απ = −βπ = (2.5 ± 1.7stat ± 0.6syst) × 10−4 fm3 .Elektromagnetska grad–a piona istražuje se Comptonovim raspršenjem π −+(A, Z) → π − + (A, Z) + γ u obrnutoj kinematici (Primakoffova reakcija) i opisuje se električnom (απ) i magnetskom polarizivošću (βπ). One ovise o krutosti piona kao složene čestice. Vrijednosti pionske polarizivosti izvode se usporedbom diferencijalnih udarnih presjeka za točkaste pione s eksperimentalnima. Mjerenje pionske polarizivosti načinili smo sa snopom π − energije 190 GeV. Snažan snop, dobro razlučivanje spektrometra, velika moć brzog bilježenja i veliko prihvaćanje podataka, te primjena pionskog i mionskog snopa jedinstvene su odlike eksperimenta COMPASS, i to omogućuje točna mjerenja polarizivosti piona Primakoffovom reakcijom. Prethodni ishodi mjerenja za pionske polarizivosti, uz pretpostavku απ + βπ = 0, su απ = −βπ = (2.5 ± 1.7stat ± 0.6syst) × 10−4 fm3

Cation Transporters of Candida albicans—New Targets to Fight Candidiasis?

Candidiasis is the wide-spread fungal infection caused by numerous strains of yeast, with the prevalence of Candida albicans. The current treatment of candidiasis is becoming rather ineffective and costly owing to the emergence of resistant strains; hence, the exploration of new possible drug targets is necessary. The most promising route is the development of novel antibiotics targeting this pathogen. In this review, we summarize such candidates found in C. albicans and those involved in the transport of (metal) cations, as the latter are essential for numerous processes within the cell; hence, disruption of their fluxes can be fatal for C. albicans

RF-Separated Beam Project for the M2 Beam Line at CERN

Within the framework of the Physics Beyond Colliders initiative at CERN, discussions are underway on the feasibility of producing radio-frequency (RF) separated beams for Phase-2 of the AMBER experiment at the M2 beam line in the North experimental area of the CERN SPS. The technique of RF separation is applied to enrich the content of a certain particle type within a beam consisting of different species at the same momentum. It relies on the fact that each particle type has a different velocity, decreasing with rest mass. The successor of the COMPASS experiment, AMBER, requires for its Phase-2 measurements high-intensity, high-purity kaon (and antiproton) beams, which cannot be delivered with the currently existing conventional M2 beam line. The present contribution introduces the principle of RF separation and explains its dependence on different parameters of beam optics and hardware. The first examination of potential showstoppers for the RF-separated beam implementation is presented, based on the particle production rates, beam line transmission for specific optics settings, limitations for overall beam intensity and purity posed by beam line acceptance and radiation protection. Different beam optics settings have been examined, providing either focused or parallel beams inside the RF cavities. The separation and transmission capability of the different optics settings for realistic characteristics of RF cavities are discussed and the preliminary results of the potential purity and intensity of the RF-separated beam are presented. They illustrate the high importance of an RF-separated kaon beam for many of the AMBER Phase-2 data taking programs, such as spectroscopy, prompt-photon production, Primakoff reactions and kaon charge-radius measurement