The detectors of the SHiP experiment at CERN

SHiP is a proposed general purpose fixed target facility at the CERN SPS accelerator. The main focus will be the physics of the Hidden Sector, \textit{i.e.} search for heavy neutrinos, dark photons and other long lived very weakly interacting particles. A dedicated detector, based on a long vacuum tank followed by a spectrometer and particle identification detectors, will allow probing a variety of models with exotic particles in the GeV mass range. Another dedicated detector will allow the study of Standard Model neutrino cross-sections and angular distribution, and allow detection of light dark matter with world leading sensitivity.Comment: 2 pages, 3 figures. Proceedings of the 14th Pisa meeting on Advanced Detector

‘Of Mice and Poets’. Callimaco e Virgilio in Orazio, sat. II 6

La Satira II 6 di Orazio contiene alcuni sottili riferimenti a passi importanti degli Aitia callimachei e delle Bucoliche virgiliane. Questi riferimenti sono attivi anche nei versi finali della satira dove il topo di campagna saluta il topo di città, e danno alla conclusione della anilis fabella di Cervio un significato non solo etico, ma anche metapoetico. Il rapporto di Orazio con i suoi predecessori è trattato con ironia e auto-ironia, e non implica un’adesione totale ai loro principi poetici. Horace’s Satire II 6 contains a few subtle references to important passages of Callimachus’ Aitia and Vergil’s Eclogues. These references also occur in the two final verses of the Satire where the country mouse says farewell to the city mouse; they provide the ending of Cervius’ anilis fabella with a meaning that is not only ethical, but also metapoetical. Horace’s relationship with his predecessors and models is treated with irony and self-irony, and does not imply a total acceptance of their poetic stances

Search for New Physics in SHiP and at future colliders

SHiP is a newly proposed fixed-target experiment at the CERN SPS with the aim of searching for hidden particles that interact very weakly with SM particles. The work presented in this document investigates SHiP's physics reach in the parameter space of the Neutrino Minimal Standard Model ($\nu$MSM), which is a theory that could solve most problems left open by the Standard Model with sterile neutrinos. A model introducing an extra $U(1)$ symmetry in the hidden sector, providing a natural candidate for dark matter, is also explored. This work shows that the SHiP experiment can improve by several orders of magnitude the sensitivity to Heavy Neutral Leptons below 2 GeV, scanning a large part of the parameter space below the $B$ meson mass. The remainder of the $\nu$MSM parameter space, dominated by right-handed neutrinos with masses above 2 GeV, can be explored at a future $e^+e^-$ collider. Similarly, SHiP can greatly improve present constraints on $U(1)$ dark photons.Comment: Proceedings for the INFIERI 2014 schoo

Testing lepton flavour universality in semileptonic Λb→Λc∗\Lambda_b \to \Lambda_c^* decays

Lepton Flavour Universality tests with semileptonic $\Lambda_b\to\Lambda_c^*$ decays are important to corroborate the present anomalies in the similar ratios $R_{D^{(*)}}$, and can provide complementary constraints on possible origins of these anomalies beyond the Standard Model. In this paper we provide - for the first time - all the necessary theoretical ingredients to perform and interpret measurements of $R_{\Lambda_c^*}$ at the LHCb experiment. For this, we revisit the heavy-quark expansion of the relevant hadronic matrix elements, and provide their expressions to order $\alpha_s$ and $1/m$ accuracy. Moreover, we study the sensitivity to the form factor parameters given the projected size and purity of upcoming and future LHCb datasets of $\Lambda_b\to \Lambda_c^*\mu\bar{\nu}$ decays. We demonstrate explicitly the need to perform a simultaneous fit to both $\Lambda_c^*$ final states. Finally, we provide projections for the uncertainty of $R_{\Lambda_c^*}$ based on the form factor analysis from semimuonic decays and theoretical relations based on the heavy-quark expansion.Comment: 27 pages, 6 figures. v2: Fixed error in subleading IW function, added supplementary information; conclusions unchange

Heavy neutrino searches from MeV to TeV

The Standard Model (SM) describes particle physics with great precision. However, it does not account for the generation of neutrino masses, whose nature we do not understand. Both a Dirac and a Majorana mass term could intervene, leading to the existence of heavy partners of the SM neutrinos, presumably more massive and nearly sterile. For suitable choices of parameters, heavy neutrinos can also provide dark matter candidates, and generate the observed baryon asymmetry of the universe. Heavy neutrinos can be searched for at beam dump facilities such as the proposed SHiP experiment if their mass is of the order of few GeV, or at high energy lepton colliders, such as the Future e+e− Circular Collider, FCC-ee, presently under study at CERN, for higher masses. This contribution presents a review of the sensitivities for heavy neutrino searches at SHiP and FCC-ee

Luminosity at LHCb in Run 3

The LHCb detector optimised its performance in Runs~1 and~2 by stabilising the instantaneous luminosity during a fill. This was achieved by tuning the distance between the two colliding beams according to the measurement of instantaneous luminosity from hardware-based trigger counters. The upgraded LHCb detector operates at fivefold instantaneous luminosity compared to the previous runs, and it has a fully software-based trigger. Consequently, a new approach to the luminosity measurement is adopted. New counters, with particular attention to maximum stability in time, and a new dedicated detector have been introduced for Run~3. Additionally, in order to verify linearity from calibration to data taking conditions, per-fill emittance scans are performed. We present an overview of the newly implemented methods for luminosity measurement, as well as early achievements obtained during the first few weeks of data taking.Comment: Proceedings of the International Conference on High Energy Physics (ICHEP) 202

Observation of the B0→ρ0ρ0{B^0 \to \rho^0 \rho^0} decay from an amplitude analysis of B0→(π+π−)(π+π−){B^0 \to (\pi^+\pi^-)(\pi^+\pi^-)} decays

Proton-proton collision data recorded in 2011 and 2012 by the LHCb experiment, corresponding to an integrated luminosity of 3.0\invfb, are analysed to search for the charmless ${B^0 \to \rho^0 \rho^0}$ decay. More than 600 ${B^0 \to (\pi^+\pi^-)(\pi^+\pi^-)}$ signal decays are selected and used to perform an amplitude analysis from which the ${B^0 \to \rho^0 \rho^0}$ decay is observed for the first time with 7.1 standard deviations significance. The fraction of ${B^0 \to \rho^0 \rho^0}$ decays yielding a longitudinally polarised final state is measured to be $f_L = 0.745^{+0.048}_{-0.058} ({\rm stat}) \pm 0.034 ({\rm syst})$. The ${B^0 \to \rho^0 \rho^0}$ branching fraction, using the ${B^0 \to \phi K^*(892)^{0}}$ decay as reference, is also reported as ${B(B^0 \to \rho^0 \rho^0) = (0.94 \pm 0.17 ({\rm stat}) \pm 0.09 ({\rm syst}) \pm 0.06 ({\rm BF})) \times 10^{-6}}$

Measurement of CPCP asymmetries and polarisation fractions in Bs0→K∗0Kˉ∗0B_s^0 \rightarrow K^{*0}\bar{K}{}^{*0} decays

An angular analysis of the decay $B_s^0 \rightarrow K^{*0}\bar{K}{}^{*0}$ is performed using $pp$ collisions corresponding to an integrated luminosity of $1.0$ ${fb}^{-1}$ collected by the LHCb experiment at a centre-of-mass energy $\sqrt{s} = 7$ TeV. A combined angular and mass analysis separates six helicity amplitudes and allows the measurement of the longitudinal polarisation fraction $f_L = 0.201 \pm 0.057 {(stat.)} \pm 0.040{(syst.)}$ for the $B_s^0 \rightarrow K^*(892)^0 \bar{K}{}^*(892)^0$ decay. A large scalar contribution from the $K^{*}_{0}(1430)$ and $K^{*}_{0}(800)$ resonances is found, allowing the determination of additional $CP$ asymmetries. Triple product and direct $CP$ asymmetries are determined to be compatible with the Standard Model expectations. The branching fraction $\mathcal{B}(B_s^0 \rightarrow K^*(892)^0 \bar{K}{}^*(892)^0)$ is measured to be $(10.8 \pm 2.1 {\ \rm (stat.)} \pm 1.4 {\ \rm (syst.)} \pm 0.6 \ (f_d/f_s) ) \times 10^{-6}$

A facility to Search for Hidden Particles (SHiP) at the CERN SPS

A new general purpose fixed target facility is proposed at the CERN SPS accelerator which is aimed at exploring the domain of hidden particles and make measurements with tau neutrinos. Hidden particles are predicted by a large number of models beyond the Standard Model. The high intensity of the SPS 400~GeV beam allows probing a wide variety of models containing light long-lived exotic particles with masses below ${\cal O}$(10)~GeV/c$^2$, including very weakly interacting low-energy SUSY states. The experimental programme of the proposed facility is capable of being extended in the future, e.g. to include direct searches for Dark Matter and Lepton Flavour Violation.Comment: Technical Proposa