Search for new physics with the SHiP experiment at CERN

SHiP is a new general purpose fixed target experiment at the CERN SPS designed to complement LHC experiments in the search for new physics. In its initial phase, the $400$ GeV proton beam extracted from the SPS will be dumped on a heavy target with the aim of integrating $2\times10^{20}$ pot in 5 years. Shielded by an active muon shield, a dedicated detector, based on a long decay volume followed by a spectrometer and particle identification detectors, will allow probing a variety of models with light long-lived exotic particles with masses below $\mathcal{O}(10)\; \mathrm{GeV}/{c^2}$. The main focus will be the physics of the so-called Hidden Portals, i.e. search for Dark Photons, Light scalars and pseudo-scalars, and Heavy Neutral Leptons. The sensitivity to Heavy Neutral Leptons will allow for the first time to probe, in the mass range above the kaon mass, a coupling range for which Baryogenesis and active neutrino masses could also be explained. A dedicated emulsion-based detector will allow detection of light dark matter in an unexplored parameter range.Comment: 6 pages, 3 figures, to appear in the Proceedings of the EPS Conference on High Energy Physics (EPS-HEP), Venice, July 2017; v2: as accepted for publication, rephrased section 3.3 in response to reviewer comment

The DUNE vertical drift TPC

The DUNE experiment is a future long-baseline neutrino oscillation experiment aiming at measuring the neutrino CP-violating phase and establishing the neutrino mass hierarchy, as well as at a rich physics programme from supernovae over low-energy physics to beyond Standard Model searches. The baseline technology for the first far detector is a proven single-phase horizontal-drift liquid-Argon TPC based on standard wire-chamber technology. For the second far detector, a new technology, the so-called "vertical drift" TPC is currently being developed: It aims at combining the strengths of the two technologies tested in the ProtoDUNE cryostats at the CERN neutrino platform, the proven horizontal-drift single-phase TPC and the ambitious vertical-drift dual-phase TPC, into a single design, a vertical-drift single-phase liquid-Argon TPC using a novel perforated-PCB anode design. This design maintains excellent tracking and calorimetry performance while significantly simplifying the complexity of the TPC construction. This paper introduces the concept of the vertical drift TPC, presents first results from small-scale prototypes and a first full-scale anode module, and outlines the plans for future prototypes and the next steps towards the full second DUNE far detector.Comment: 6 pages, 5 figures. Submitted as proceedings for ICHEP22; v2: fix some typos and minor grammar mistakes for final versio

Multidifferential study of identified charged hadron distributions in ZZ-tagged jets in proton-proton collisions at s=\sqrt{s}=13 TeV

Jet fragmentation functions are measured for the first time in proton-proton collisions for charged pions, kaons, and protons within jets recoiling against a $Z$ boson. The charged-hadron distributions are studied longitudinally and transversely to the jet direction for jets with transverse momentum 20 $< p_{\textrm{T}} < 100$ GeV and in the pseudorapidity range $2.5 < \eta < 4$. The data sample was collected with the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 1.64 fb$^{-1}$. Triple differential distributions as a function of the hadron longitudinal momentum fraction, hadron transverse momentum, and jet transverse momentum are also measured for the first time. This helps constrain transverse-momentum-dependent fragmentation functions. Differences in the shapes and magnitudes of the measured distributions for the different hadron species provide insights into the hadronization process for jets predominantly initiated by light quarks.Comment: All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb public pages

Study of the B−→Λc+Λˉc−K−B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-} decay

The decay $B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-}$ is studied in proton-proton collisions at a center-of-mass energy of $\sqrt{s}=13$ TeV using data corresponding to an integrated luminosity of 5 $\mathrm{fb}^{-1}$ collected by the LHCb experiment. In the $\Lambda_{c}^+ K^{-}$ system, the $\Xi_{c}(2930)^{0}$ state observed at the BaBar and Belle experiments is resolved into two narrower states, $\Xi_{c}(2923)^{0}$ and $\Xi_{c}(2939)^{0}$, whose masses and widths are measured to be $$m(\Xi_{c}(2923)^{0}) = 2924.5 \pm 0.4 \pm 1.1 \,\mathrm{MeV}, \\ m(\Xi_{c}(2939)^{0}) = 2938.5 \pm 0.9 \pm 2.3 \,\mathrm{MeV}, \\ \Gamma(\Xi_{c}(2923)^{0}) = \phantom{000}4.8 \pm 0.9 \pm 1.5 \,\mathrm{MeV},\\ \Gamma(\Xi_{c}(2939)^{0}) = \phantom{00}11.0 \pm 1.9 \pm 7.5 \,\mathrm{MeV},$$ where the first uncertainties are statistical and the second systematic. The results are consistent with a previous LHCb measurement using a prompt $\Lambda_{c}^{+} K^{-}$ sample. Evidence of a new $\Xi_{c}(2880)^{0}$ state is found with a local significance of $3.8\,\sigma$, whose mass and width are measured to be $2881.8 \pm 3.1 \pm 8.5\,\mathrm{MeV}$ and $12.4 \pm 5.3 \pm 5.8 \,\mathrm{MeV}$, respectively. In addition, evidence of a new decay mode $\Xi_{c}(2790)^{0} \to \Lambda_{c}^{+} K^{-}$ is found with a significance of $3.7\,\sigma$. The relative branching fraction of $B^{-} \to \Lambda_{c}^{+} \bar{\Lambda}_{c}^{-} K^{-}$ with respect to the $B^{-} \to D^{+} D^{-} K^{-}$ decay is measured to be $2.36 \pm 0.11 \pm 0.22 \pm 0.25$, where the first uncertainty is statistical, the second systematic and the third originates from the branching fractions of charm hadron decays.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-028.html (LHCb public pages

Measurement of the ratios of branching fractions R(D∗)\mathcal{R}(D^{*}) and R(D0)\mathcal{R}(D^{0})

The ratios of branching fractions $\mathcal{R}(D^{*})\equiv\mathcal{B}(\bar{B}\to D^{*}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(\bar{B}\to D^{*}\mu^{-}\bar{\nu}_{\mu})$ and $\mathcal{R}(D^{0})\equiv\mathcal{B}(B^{-}\to D^{0}\tau^{-}\bar{\nu}_{\tau})/\mathcal{B}(B^{-}\to D^{0}\mu^{-}\bar{\nu}_{\mu})$ are measured, assuming isospin symmetry, using a sample of proton-proton collision data corresponding to 3.0 fb${ }^{-1}$ of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode $\tau^{-}\to\mu^{-}\nu_{\tau}\bar{\nu}_{\mu}$. The measured values are $\mathcal{R}(D^{*})=0.281\pm0.018\pm0.024$ and $\mathcal{R}(D^{0})=0.441\pm0.060\pm0.066$, where the first uncertainty is statistical and the second is systematic. The correlation between these measurements is $\rho=-0.43$. Results are consistent with the current average of these quantities and are at a combined 1.9 standard deviations from the predictions based on lepton flavor universality in the Standard Model.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-039.html (LHCb public pages

Optimisation of the SHiP experimental design

The SHiP experiment is a proposed experiment aiming to search for new super-weakly interacting particles. The concept is based on using a very intense and high energy proton beam at the CERN Super Proton Synchrotron (SPS) which is delivered to the new Beam Dump Facility (BDF), where the experiment will search for New Physics (NP) in a zero background environment. This thesis describes several studies for the optimisation of this concept, in order to maximise its physics potential. These include studies of a benchmark signal model to understand acceptance effects, studies of the muon induced background using both simulation and a dedicated experiment at the SPS, and the optimisation of the muon shield —a crucial component of SHiP— using machine learning techniques.Open Acces

Optimisation of the SHiP experimental design

The SHiP experiment is a proposed experiment aiming to search for new super-weakly interacting particles. The concept is based on using a very intense and high energy proton beam at the CERN Super Proton Synchrotron (SPS) which is delivered to the new Beam Dump Facility (BDF), where the experiment will search for New Physics (NP) in a zero background environment. This thesis describes several studies for the optimisation of this concept, in order to maximise its physics potential. These include studies of a benchmark signal model to understand acceptance effects, studies of the muon induced background using both simulation and a dedicated experiment at the SPS, and the optimisation of the muon shield —a crucial component of SHiP— using machine learning techniques

The DUNE vertical drift TPC

International audienceThe DUNE experiment is a future long-baseline neutrino oscillation experiment aiming at mea-suring the neutrino CP-violating phase and establishing the neutrino mass hierarchy, as well as ata rich physics programme from supernovae over low-energy physics to beyond Standard Modelsearches.The baseline technology for the first far detector is a proven single-phase horizontal-drift liquid-Argon TPC based on standard wire-chamber technology.For the second far detector, a new technology, the so-called “vertical drift” TPC is currently beingdeveloped: It aims at combining the strengths of the two technologies tested in the ProtoDUNEcryostats at the CERN neutrino platform, the proven horizontal-drift single-phase TPC and the ambi-tious vertical-drift dual-phase TPC, into a single design, a vertical-drift single-phase liquid-ArgonTPC using a novel perforated-PCB anode design. This design maintains excellent tracking andcalorimetry performance while significantly simplifying the complexity of the TPC construction.This paper introduces the concept of the vertical drift TPC, presents first results from small-scaleprototypes and a first full-scale anode module, and outlines the plans for future prototypes and thenext steps towards the full second DUNE far detector

The DUNE vertical drift TPC

International audienceThe DUNE experiment is a future long-baseline neutrino oscillation experiment aiming at mea-suring the neutrino CP-violating phase and establishing the neutrino mass hierarchy, as well as ata rich physics programme from supernovae over low-energy physics to beyond Standard Modelsearches.The baseline technology for the first far detector is a proven single-phase horizontal-drift liquid-Argon TPC based on standard wire-chamber technology.For the second far detector, a new technology, the so-called “vertical drift” TPC is currently beingdeveloped: It aims at combining the strengths of the two technologies tested in the ProtoDUNEcryostats at the CERN neutrino platform, the proven horizontal-drift single-phase TPC and the ambi-tious vertical-drift dual-phase TPC, into a single design, a vertical-drift single-phase liquid-ArgonTPC using a novel perforated-PCB anode design. This design maintains excellent tracking andcalorimetry performance while significantly simplifying the complexity of the TPC construction.This paper introduces the concept of the vertical drift TPC, presents first results from small-scaleprototypes and a first full-scale anode module, and outlines the plans for future prototypes and thenext steps towards the full second DUNE far detector