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

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

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

Effect of TNF-α on C. albicans Morphological Change in Liquid Media

C. albicans undergoes morphological change in order to infiltrate the epithelial cell layer, posing health threat. This morphological infectious state is known as filamentous due to the elongated protrusion that stems from the base yeast form. To date, the intestinal cues responsible for the change in C. albicans morphology are not clearly defined. Candidiasis is observed in Crohn’s disease, where elevated level of inflammatory cytokines such as tumor necrosis alpha (TNF-α) is reported. We hypothesize that TNF-α may represent an intestinal cue responsible for the shift in morphology in C. albicans. We tested our hypothesis in three different liquid media: Minimal (MM), Yeast Extract Peptone Dextrose (YEPD), and Spider media (SM). In our experimental conditions, we found that Fetal Bovine Serum (FBS) induced filamentous growth 66% of the time in SM, 16% of the time in YEPD and none in MM (n = 18 plates for each condition). While both YEPD and SM saw significant impact on filamentous growth with FBS, SM showed greater significance so this condition was used in the TNF-α study. In a preliminary study, we found that TNF-α on its own did not cause filamentation (n = 15). Yet, TNF-⍺ totally inhibited FBS-induced filamentous growth, while FBS induced 20% filamentous growth in our control (n=15). In conclusion, we found that FBS-induced filamentous growth is dependent on the type of liquid media used. In addition, our preliminary experiments show that TNF-α prevent filamentous growth and may represent a protective mechanism during candidiasis observed during Crohn’s disease

Analysis of the Systematic Errors in the Positions of BATSE Catalog Bursts

We analyze the systematic errors in the positions of bursts in the BATSE 1B, 2B and 3B catalogs, using a likelihood approach. We use the BATSE data in conjunction with 196 single IPN arcs. We assume circular Gaussian errors, and that the total error is the sum in quadrature of the systematic error $\sigma_{\rm sys}$ and statistical error $\sigma_{\rm stat}$, as prescribed by the BATSE catalog. We find that the 3B burst positions are inconsistent with the value $\sigma_{\rm sys} = 1.6^\circ$ stated in the BATSE 3B catalog.Comment: A five page LateX file that uses the Revtex conference proceedings macro aipbook.sty, and includes five postscript figures using psfig. To Be published in the Proceedings of the Third Hunstville Symposium on Gamma-Ray Bursts, eds. C. Kouveliotou, M.S. Briggs and G.J. Fishman (New York:AIP

Likelihood Methods and Classical Burster Repetition

We develop a likelihood methodology which can be used to search for evidence of burst repetition in the BATSE catalog, and to study the properties of the repetition signal. We use a simplified model of burst repetition in which a number $N_{\rm r}$ of sources which repeat a fixed number of times $N_{\rm rep}$ are superposed upon a number $N_{\rm nr}$ of non-repeating sources. The instrument exposure is explicitly taken into account. By computing the likelihood for the data, we construct a probability distribution in parameter space that may be used to infer the probability that a repetition signal is present, and to estimate the values of the repetition parameters. The likelihood function contains contributions from all the bursts, irrespective of the size of their positional errors --- the more uncertain a burst's position is, the less constraining is its contribution. Thus this approach makes maximal use of the data, and avoids the ambiguities of sample selection associated with data cuts on error circle size. We present the results of tests of the technique using synthetic data sets.Comment: 5 pages, Revtex (aipbook.sty included), 2 PostScript figures included using psfig. To appear in the Proceedings of the 1995 La Jolla Workshop "High Velocity Neutron Stars and Gamma-Ray Bursts," eds. R. Rothschild and R. Lingenfelter, AIP, New Yor

Regression Concept Vectors for Bidirectional Explanations in Histopathology

Explanations for deep neural network predictions in terms of domain-related concepts can be valuable in medical applications, where justifications are important for confidence in the decision-making. In this work, we propose a methodology to exploit continuous concept measures as Regression Concept Vectors (RCVs) in the activation space of a layer. The directional derivative of the decision function along the RCVs represents the network sensitivity to increasing values of a given concept measure. When applied to breast cancer grading, nuclei texture emerges as a relevant concept in the detection of tumor tissue in breast lymph node samples. We evaluate score robustness and consistency by statistical analysis.Comment: 9 pages, 3 figures, 3 table

X-ray ionization of the intergalactic medium by quasars

We investigate the impact of quasars on the ionization of the surrounding intergalactic medium (IGM) with the radiative transfer code \texttt{CRASH4}, now accounting for X-rays and secondary electrons. After comparing with analytic solutions, we post-process a cosmic volume ($\approx 1.5\times 10^4$ Mpc$^3 h^{-3}$) containing a ULAS J1120+0641-like quasar (QSO) hosted by a $5 \times 10^{11} {\rm M}_\odot h^{-1}$ dark matter (DM) halo. We find that: (i) the average HII region ($R\sim3.2$~pMpc in a lifetime $t_f = 10^7$~yrs) is mainly set by UV flux, in agreement with semi-analytic scaling relations; (ii) a largely neutral ($x_{\textrm{HII}} < 0.001$), warm ($T\sim 10^3$~K) tail extends up to few Mpc beyond the ionization front, as a result of the X-ray flux; (iii) LyC-opaque inhomogeneities induce a line of sight (LOS) scatter in $R$ as high as few physical Mpc, consistent with the DLA scenario proposed to explain the anomalous size of the ULAS J1120+0641 ionized region. On the other hand, with an ionization rate $\dot{N}_{\gamma,0} \sim 10^{57}$~s$^{-1}$, the assumed DLA clustering and gas opacity, only one LOS shows an HII region compatible with the observed one. We deduce that either the ionization rate of the QSO is at least one order of magnitude lower or the ULAS J1120+0641 bright phase is shorter than $10^7$~yrs.Comment: Accepted for publication in MNRAS Main Journal, Accepted 2018 May 2