LHCb Collaboration(Aaij, R. et al), Henry, L., Jashal, B. K., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2021). Search for the doubly heavy baryons Omega(0)(bc) and Xi(0)(bc) decaying to Lambda(+)(c)pi(-) and Xi(+)(c)pi-. Chin. Phys. C, 45(9), 093002–12pp.
Abstract: The first search for the doubly heavy Omega(0)(bc) baryon and a search for the Xi(0)(bc) baryon are performed using collision data collected via the experiment from 2016 to 2018 at a centre-of-mass energy of, corresponding to an integrated luminosity of 5.2 fb(-1). The baryons are reconstructed via their decays to Lambda(+)(-)(c)(pi) and Xi(+)(c)pi(-). No significant excess is found for invariant masses between 6700 and 7300 MeV/c(2), in a rapidity range from 2.0 to 4.5 and a transverse momentum range from 2 to 20 MeV/c. Upper limits are set on the ratio of the Omega(0)(bc) and Xi(0)(bc) production cross-section times the branching fraction to Lambda(+)(c)pi(-)(Xi(+)(c)pi(-)) relative to that of the Lambda(0)(b)(Xi(0)(b)) baryon, for different lifetime hypotheses, at 95% confidence level. The upper limits range from 0.5x10(-4) to 2.5x10(-4) for the Omega(0)(bc) -> Lambda(+)(c)pi(-) (Xi(0)(bc) -> Lambda(+)(c)pi(-)) decay, pending on the considered mass and lifetime of the Omega(0)(bc) (Xi(0)(bc)) baryon.
|
Borsato, M. et al, Zurita, J., Henry, L., Jashal, B. K., & Oyanguren, A. (2022). Unleashing the full power of LHCb to probe stealth new physics. Rep. Prog. Phys., 85(2), 024201–45pp.
Abstract: In this paper, we describe the potential of the LHCb experiment to detect stealth physics. This refers to dynamics beyond the standard model that would elude searches that focus on energetic objects or precision measurements of known processes. Stealth signatures include long-lived particles and light resonances that are produced very rarely or together with overwhelming backgrounds. We will discuss why LHCb is equipped to discover this kind of physics at the Large Hadron Collider and provide examples of well-motivated theoretical models that can be probed with great detail at the experiment.
|
Calefice, L., Hennequin, A., Henry, L., Jashal, B. K., Mendoza, D., Oyanguren, A., et al. (2022). Effect of the high-level trigger for detecting long-lived particles at LHCb. Front. Big Data, 5, 1008737–13pp.
Abstract: Long-lived particles (LLPs) show up in many extensions of the Standard Model, but they are challenging to search for with current detectors, due to their very displaced vertices. This study evaluated the ability of the trigger algorithms used in the Large Hadron Collider beauty (LHCb) experiment to detect long-lived particles and attempted to adapt them to enhance the sensitivity of this experiment to undiscovered long-lived particles. A model with a Higgs portal to a dark sector is tested, and the sensitivity reach is discussed. In the LHCb tracking system, the farthest tracking station from the collision point is the scintillating fiber tracker, the SciFi detector. One of the challenges in the track reconstruction is to deal with the large amount of and combinatorics of hits in the LHCb detector. A dedicated algorithm has been developed to cope with the large data output. When fully implemented, this algorithm would greatly increase the available statistics for any long-lived particle search in the forward region and would additionally improve the sensitivity of analyses dealing with Standard Model particles of large lifetime, such as KS0 or Lambda (0) hadrons.
|
LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2017). Prompt and nonprompt J/psi production and nuclear modification in pPb collisions at root s(NN)=8.16 TeV. Phys. Lett. B, 774, 159–178.
Abstract: The production of J/psi mesons is studied in proton-lead collisions at the centre-of-mass energy per nucleon pair root s(NN) = 8.16 TeV with the LHCb detector at the LHC. The double differential cross-sections of prompt and nonprompt J/psi production are measured as a function of the J/psi transverse momentum and rapidity in the nucleon-nucleon centre-of-mass frame. Forward-to-backward ratios and nuclear modification factors are determined. The results are compared with theoretical calculations based on collinear factorisation using nuclear parton distribution functions, on the colour glass condensate or on coherent energy loss models.
|
LHCb Collaboration(Aaij, R. et al), Garcia Martin, L. M., Henry, L., Martinez-Vidal, F., Oyanguren, A., Remon Alepuz, C., et al. (2018). First observation of forward Z -> b(b)over-bar production in pp collisions at root s=8 TeV. Phys. Lett. B, 776, 430–439.
Abstract: The decay Z -> b (b) over bar is reconstructed in pp collision data, corresponding to 2 fb(-1) of integrated luminosity, collected by the LHCb experiment at a centre-of-mass energy of root s = 8 TeV. The product of the Z production cross-section and the Z -> b (b) over bar branching fraction is measured for candidates in the fiducial region defined by two particle-level b-quark jets with pseudorapidities in the range 2.2 < eta < 4.2, with transverse momenta p(T) > 20 GeV and dijet invariant mass in the range 45 < m(jj) < 165 GeV. From a signal yield of 5462 +/- 763 Z -> b (b) over bar events, where the uncertainty is statistical, a production cross-section times branching fraction of 332 +/- 46 +/- 59 pb is obtained, where the first uncertainty is statistical and the second systematic. The measured significance of the signal yield is 6.0 standard deviations. This measurement represents the first observation of the Z -> b (b) over bar production in the forward region of pp collisions.
|
