Fixed target measurements at LHCb for cosmic rays physics

The LHCb experiment has the unique possibility, among the LHC experiments, to be operated in fixed target mode, using its internal gas target. The energy scale achievable at the LHC, combined with the LHCb forward geometry and detector capabilities, allow to explore particle production in a wide Bjorken-$x$ range at the $\sqrt{s_{\scriptscriptstyle\rm NN}} \sim 100$ GeV energy scale, providing novel inputs to nuclear and cosmic ray physics. The first measurement of antiproton production in collisions of LHC protons on helium nuclei at rest is presented. The knowledge of this cross-section is of great importance for the study of the cosmic antiproton flux, and the LHCb results are expected to improve the interpretation of the recent high-precision measurements of cosmic antiprotons performed by the space-borne PAMELA and AMS-02 experiments.Comment: Proceedings for the 52nd Rencontres de Moriond EW 201

Clumping factors of HII, HeII and HeIII

Estimating the intergalactic medium ionization level of a region needs proper treatment of the reionization process for a large representative volume of the universe. The clumping factor, a parameter which accounts for the effect of recombinations in unresolved, small-scale structures, aids in achieving the required accuracy for the reionization history even in simulations with low spatial resolution. In this paper, we study for the first time the redshift evolution of clumping factors of different ionized species of H and He in a small but very high resolution simulation of the reionization process. We investigate the dependence of the value and redshift evolution of clumping factors on their definition, the ionization level of the gas, the grid resolution, box size and mean dimensionless density of the simulations.Comment: 12 pages, 10 figures, 1 table. Accepted by MNRA

Determining the Gamma-Ray Burst Rate as a Function of Redshift

We exploit the 14 gamma-ray bursts (GRBs) with known redshifts $z$ and the 7 GRBs for which there are constraints on $z$ to determine the GRB rate $R_{\rm GRB}(z)$, using a method based on Bayesian inference. We find that, despite the qualitative differences between the observed GRB rate and estimates of the SFR in the universe, current data are consistent with $R_{\rm GRB}(z)$ being proportional to the SFR.Comment: 3 pages, 3 figures, to appear in AIP proc. "Gamma-Ray Burst and Afterglow Astronomy 2001" Woods Hole, Massachusett

Results on heavy ion physics at LHCb

In the last years, the \lhcb experiment established itself as an important contributor to heavy ion physics by exploiting some of its specific features. Production of particles, notably heavy flavour states, can be studied in p-p, p-Pb and Pb-Pb collisions at LHC energies in the forward rapidity region (pseudorapidity between 2 and 5), providing measurements which are highly complementary to the other LHC experiments. Moreover, owing to its forward geometry, the detector is also well suited to study fixed-target collisions, obtained by impinging the LHC beams on gas targets with different mass numbers. In this configuration, p-A collisions can be studied at the relatively unexplored scale of sqrt(sNN) ~ 100 GeV, also providing valuable inputs to cosmic ray physics. An overview of the measurements obtained so far by the LHCb ion program is presented.Comment: on behalf of the LHCb collaboration. Prepared for the fifth biennial "Workshop on Discovery Physics at the LHC" (Kruger2018), 3-7 December 2018, Hazyview (South Africa

Are The Four Gamma-Ray Bursts of 1996 October 27-29 Due to Repetition of a Single Source?

BATSE, Ulysses, and TGRS and KONUS on WIND detected four gamma-ray events within 1.8 days during 1996 October 27-29, consistent with coming from the same location on the sky. We assess the evidence that these events may be due to a series of bursts from a single source by calculating the probability that such a clustering in position and in time of occurrence might happen by chance. The calculation of this probability is afflicted by the usual problem of a posteriori statistics. We introduce a clustering statistic, which is formed from the "minimum circle radius" (i.e. the radius of the smallest circle that just encloses the positions of all the events) and the minimum time lapse (i.e. the time elapsed between the first and last event). We also introduce a second clustering statistic, which is formed from the "cluster likelihood function" and the minimum time lapse. We show that the use of these statistics largely eliminates the "a posteriori" nature of the problem. The two statistics yield significances of the clustering of $3.3\times 10^{-4}$ and $3.1\times 10^{-5}$, respectively, if we interpret the four events as four bursts, whereas the clustering is not significant if we interpret the four events as only three bursts. However, in the latter case one of the bursts is the longest ever observed by BATSE.Comment: 5 pages, 1 PostScript figure. Uses AIP conference proceedings LaTeX macros. To appear in the Proceedings of the Fourth Huntsville Gamma-Ray Burst Symposiu

Recent LHCb Results

The LHCb experiment started its physics program with the 37/pb of pp collisions at 7 TeV c.m. energy delivered by the LHC during 2010. The performances and capability of the experiment, conceived for precision measurements in the heavy flavour sector, are illustrated through the first results from the experimental core program. A rich set of production studies provide precision QCD and EW tests in the unique high rapidity region covered by LHCb. Notably, results for W and Z production are very encouraging for setting constraints on the parton PDFs.Comment: Proceedings for the "XIX International Workshop on Deep-Inelastic Scattering and Related Subjects" (DIS2011), Newport News (USA), April 11th -15th 201

BiHom-Associative Algebras, BiHom-Lie Algebras and BiHom-Bialgebras

A BiHom-associative algebra is a (nonassociative) algebra $A$ endowed with two commuting multiplicative linear maps $\alpha,\beta\colon A\rightarrow A$ such that $\alpha (a)(bc)=(ab)\beta (c)$, for all $a, b, c\in A$. This concept arose in the study of algebras in so-called group Hom-categories. In this paper, we introduce as well BiHom-Lie algebras (also by using the categorical approach) and BiHom-bialgebras. We discuss these new structures by presenting some basic properties and constructions (representations, twisted tensor products, smash products etc)