Observation of a J^PC = 1-+ exotic resonance in diffractive dissociation of 190 GeV/c pi- into pi- pi- pi+

The COMPASS experiment at the CERN SPS has studied the diffractive dissociation of negative pions into the pi- pi- pi+ final state using a 190 GeV/c pion beam hitting a lead target. A partial wave analysis has been performed on a sample of 420000 events taken at values of the squared 4-momentum transfer t' between 0.1 and 1 GeV^2/c^2. The well-known resonances a1(1260), a2(1320), and pi2(1670) are clearly observed. In addition, the data show a significant natural parity exchange production of a resonance with spin-exotic quantum numbers J^PC = 1-+ at 1.66 GeV/c^2 decaying to rho pi. The resonant nature of this wave is evident from the mass-dependent phase differences to the J^PC = 2-+ and 1++ waves. From a mass-dependent fit a resonance mass of 1660 +- 10+0-64 MeV/c^2 and a width of 269+-21+42-64 MeV/c^2 is deduced.Comment: 7 page, 3 figures; version 2 gives some more details, data unchanged; version 3 updated authors, text shortened, data unchange

Search for strongly interacting massive particles generating trackless jets in proton-proton collisions at s = 13 TeV

A search for dark matter in the form of strongly interacting massive particles (SIMPs) using the CMS detector at the LHC is presented. The SIMPs would be produced in pairs that manifest themselves as pairs of jets without tracks. The energy fraction of jets carried by charged particles is used as a key discriminator to suppress efficiently the large multijet background, and the remaining background is estimated directly from data. The search is performed using proton-proton collision data corresponding to an integrated luminosity of 16.1 fb - 1 , collected with the CMS detector in 2016. No significant excess of events is observed above the expected background. For the simplified dark matter model under consideration, SIMPs with masses up to 100 GeV are excluded and further sensitivity is explored towards higher masses

Study of the pi(0)pi(0) system in pp central collisions at 450 GeV/c

The effective mass spectrum of pi(0) pairs produced in pp central collisions (pp --> pf pi(0) pi(0)p(s)) at 450 GeV/c, root s = 29 GeV, below 1 GeV differs from that observed in peripheral charge exchange reactions, In particular, there is a large number of events between pi pi-threshold and 1 GeV, that interfere with f(0)(980) destructively. The possible existence of a broad S-wave state is suggested. (C) 1997 Published by Elsevier Science B.V

GAMS RESULTS ON THE OMEGA-PI(0) SYSTEM

The first results on the omega-pi-0 system produced in the charge-exchange reaction of pi--p scattering at 38 GeV/c and 100 GeV/c are presented. The omega-pi-0 mass spectrum shows, alongside with the well-known b1(0) (1235) and rho-3(0) (1690) mesons, a new neutral state with mass 2200 +/- 20 MeV and width 260 +/- 50 MeV. This meson, X(2200), is produced like rho-3 through one-pion exchange. X(2200) is a candidate for the 1-- multiplet, and its possible interpretation is a 2(3)D1 excitation of the rho-0. Its production cross section at 3 S GeV/c is equal to sigma(pi--p --> Xn) . BR (X --> omega-pi-0) = 120 +/- 25 nb. Cross sections for b1 and rho-3 have also been measured. The energy dependences have been determined

NEW GAMS RESULTS ON MESON SPECTROSCOPY

Results on meson spectroscopy obtained in 1993 by the GAMS Collaboration are presented. Model-independent measurements of the omega --> etagamma decay branching ratio, as well as the observation of the X(1740) state in the K(s)0K(s)0 decay mode, are considered. The results on the partial-wave analysis of the omegapi0 and pi0pi0 systems produced at small momentum transfer in pi-p charge-exchange reactions are discussed. The experiments on resonant etaeta-system production on a central region of the pp interaction are also discussed

A study of the centrally produced pi(+)pi(-)pi(0)channel in pp interactions at 450 GeV/c

The reaction pp –> p(f)(pi(+)pi(-)pi(0))p(s) has been studied at 450 GeV/c in an experiment designed to search for gluonic status. A spin analysis has been performed and the dP(T) filter applied. The analysis confirms the previous observation that all undisputed (<q(q)over bar> states are suppressed at small dP(T). In addition, a clear difference is observed in the production mechanism for the eta and omega. (C) 1998 Elsevier Science B.V