Searches for low-mass dimuon resonances

Abstract

Searches are performed for a low-mass dimuon resonance, X, produced in proton-proton collisions at a center-of-mass energy of 13 TeV, using a data sample corresponding to an integrated luminosity of 5.1 fb−1 and collected with the LHCb detector. The X bosons can either decay promptly or displaced from the proton-proton collision, where in both cases the requirements placed on the event and the assumptions made about the production mechanisms are kept as minimal as possible. The searches for promptly decaying X bosons explore the mass range from near the dimuon threshold up to 60 GeV, with nonnegligible X widths considered above 20 GeV. The searches for displaced X → μ+μ− decays consider masses up to 3 GeV. None of the searches finds evidence for a signal and 90% confidence-level exclusion limits are placed on the X → μ+μ− cross sections, each with minimal model dependence. In addition, these results are used to place world-leading constraints on GeV-scale bosons in the two-Higgs-doublet and hidden-valley scenarios.

Multi-track displaced vertices at B-factories

“…LHCb only have sensitivity for LLP masses above approximately 20 GeV [101,102] because the large vertex mass can be used to efficiently reject B backgrounds, although the reconstruction of displaced resonances is possible at lower masses [51]. While it is possible for LHCb to improve on low-mass exclusive and inclusive signatures [103,104] and this merits further study, we nevertheless expect Belle II to have a unique role in covering intermediate-lifetime hidden sectors in an inclusive manner.…”

“…Furthermore, only a limited number of these searches currently exist at B-factories [42,47,49], and because a significant amount of work has been done at the LHC to generalize and expand the scope of LLP searches [39,50], much of this knowledge gained can be applied to Bfactories as well. We propose several extensions of existing searches for LLPs at BABAR [49] and LHCb [51], both of which are inclusive with respect to production mechanism but require exclusive reconstruction of 2-body decays: our proposals include searching for displaced vertices (DVs) with more than two tracks or two DVs in an event. Because of these more stringent selection criteria, such searches can relax other aspects of the analysis, such as prompt objects associated with the specific LLP production mechanism, or the exclusive reconstruction of the LLP mass; this allows a significant broadening of the applicability of the searches.…”

Exploring new possibilities to discover a light pseudo-scalar at LHCb

“…Rare meson decays, in fact, provide an additional class of strong bounds [7][8][9][10]. At the LHC, low masses are mainly constrained by di-muon [11][12][13][14][15] and di-photon searches [16][17][18][19][20][21]. a e-mail: buarque@chalmers.se b e-mail: g.cacciapaglia@ipnl.in2p3.fr c e-mail: xabier.cid.vidal@cern.ch d e-mail: gabriele.ferretti@chalmers.se e e-mail: tom.flacke@gmail.com f e-mail: carlos.vazquez@cern.ch (corresponding author)…”

Portal Effective Theories. A framework for the model independent description of light hidden sector interactions

“…[63][64][65], the latter can couple only very weakly to the SM fields. Besides the high intensity data sets of CMS [66][67][68], ATLAS [69] and LHCb [70][71][72][73][74][75][76], and the high luminosity runs of the Large Hadron Collider (LHC) [77], which are optimised for such searches, these particles could be produced in large quantities via The PET framework extends a given EFT of the SM by combining its operators with portal operators that couple the SM DOFs to messenger fields that are dynamic at the relevant energy scale. The portal operators O portal nm can be collected into a set of portal currents J portal n that allow for a spurion analysis and for e.g.…”