Centro Científico Tecnológico de Valparaíso

This paper describes the physics case for a new fixed target facility at CERN SPS. The SHiP (search for hidden particles) experiment is intended to hunt for new physics in the largely unexplored domain of very weakly interacting particles with masses below the Fermi scale, inaccessible to the LHC experiments, and to study tau neutrino physics. The same proton beam setup can be used later to look for decays of tau-leptons with lepton flavour number non-conservation, [Formula: see text] and to search for weakly-interacting sub-GeV dark matter candidates. We discuss the evidence for physics beyond the standard model and describe interactions between new particles and four different portals-scalars, vectors, fermions or axion-like particles. We discuss motivations for different models, manifesting themselves via these interactions, and how they can be probed with the SHiP experiment and present several case studies. The prospects to search for relatively light SUSY and composite particles at SHiP are also discussed. We demonstrate that the SHiP experiment has a unique potential to discover new physics and can directly probe a number of solutions of beyond the standard model puzzles, such as neutrino masses, baryon asymmetry of the Universe, dark matter, and inflation.

This report reviews the study of open heavy-flavour and quarkonium production in high-energy hadronic collisions, as tools to investigate fundamental aspects of Quantum Chromodynamics, from the proton and nucleus structure at high energy to deconfinement and the properties of the Quark-Gluon Plasma. Emphasis is given to the lessons learnt from LHC Run 1 results, which are reviewed in a global picture with the results from SPS and RHIC at lower energies, as well as to the questions to be addressed in the future. The report covers heavy flavour and quarkonium production in proton-proton, proton-nucleus and nucleus-nucleus collisions. This includes discussion of the effects of hot and cold strongly interacting matter, quarkonium photoproduction in nucleus-nucleus collisions and perspectives on the study of heavy flavour and quarkonium with upgrades of existing experiments and new experiments. The report results from the activity of the SaporeGravis network of the I3 Hadron Physics programme of the European Union 7[Formula: see text] Framework Programme.

We examine the theoretical motivations for long-lived particle (LLP) signals at the LHC in a comprehensive survey of standard model (SM) extensions. LLPs are a common prediction of a wide range of theories that address unsolved fundamental mysteries such as naturalness, dark matter, baryogenesis and neutrino masses, and represent a natural and generic possibility for physics beyond the SM (BSM). In most cases the LLP lifetime can be treated as a free parameter from the [Formula: see text]m scale up to the Big Bang Nucleosynthesis limit of [Formula: see text] m. Neutral LLPs with lifetimes above [Formula: see text]100 m are particularly difficult to probe, as the sensitivity of the LHC main detectors is limited by challenging backgrounds, triggers, and small acceptances. MATHUSLA is a proposal for a minimally instrumented, large-volume surface detector near ATLAS or CMS. It would search for neutral LLPs produced in HL-LHC collisions by reconstructing displaced vertices (DVs) in a low-background environment, extending the sensitivity of the main detectors by orders of magnitude in the long-lifetime regime. We study the LLP physics opportunities afforded by a MATHUSLA-like detector at the HL-LHC, assuming backgrounds can be rejected as expected. We develop a model-independent approach to describe the sensitivity of MATHUSLA to BSM LLP signals, and compare it to DV and missing energy searches at ATLAS or CMS. We then explore the BSM motivations for LLPs in considerable detail, presenting a large number of new sensitivity studies. While our discussion is especially oriented towards the long-lifetime regime at MATHUSLA, this survey underlines the importance of a varied LLP search program at the LHC in general. By synthesizing these results into a general discussion of the top-down and bottom-up motivations for LLP searches, it is our aim to demonstrate the exceptional strength and breadth of the physics case for the construction of the MATHUSLA detector.

Inflammation contributes to neurodegeneration in post-ischemic brain, diabetes, and Alzheimer's disease. Participants in this inflammatory response include activation of microglia and astrocytes. We studied the role of microglia treated with amyloid-β peptide (Aβ) on hemichannel activity of astrocytes subjected to hypoxia in high glucose. Reoxygenation after 3 h hypoxia in high glucose induced transient astroglial permeabilization via Cx43 hemichannels and reduction in intercellular communication via Cx43 cell-cell channels. Both responses were greater and longer lasting in astrocytes previously exposed for 24 h to conditioned medium from Aβ-treated microglia (CM-Aβ). The effects of CM-Aβ were mimicked by TNF-α and IL-1β and were abrogated by neutralizing TNF-α with soluble receptor and IL-1β with a receptor antagonist. Astrocytes under basal conditions protected neurons against hypoxia, but exposure to CM-Aβ made them toxic to neurons subjected to a sub-lethal hypoxia/reoxygenation episode, revealing the additive nature of the insults. Astrocytes exposed to CM-Aβ induced permeabilization of cortical neurons through activation of neuronal pannexin 1 (Panx1) hemichannels by ATP and glutamate released through astroglial Cx43 hemichannels. In agreement, inhibition of NMDA or P2X receptors only partially reduced the activation of neuronal Panx1 hemichannels and neuronal mortality, but simultaneous inhibition of both receptors completely prevented the neurotoxic response. Therefore, we suggest that responses to ATP and glutamate converge in activation of neuronal Panx1 hemichannels. Thus, we propose that blocking hemichannels expressed by astrocytes and/or neurons in the inflamed nervous system could represent a novel and alternative strategy to reduce neuronal loss in various pathological states including Alzheimer's disease, diabetes and ischemia.

The mechanisms involved in Alzheimer's disease are not completely understood and how glial cells contribute to this neurodegenerative disease remains to be elucidated. Because inflammatory treatments and products released from activated microglia increase glial hemichannel activity, we investigated whether amyloid-β peptide (Aβ) could regulate these channels in glial cells and affect neuronal viability. Microglia, astrocytes, or neuronal cultures as well as acute hippocampal slices made from GFAP-eGFP transgenic mice were treated with the active fragment of Aβ. Hemichannel activity was monitored by single-channel recordings and by time-lapse ethidium uptake, whereas neuronal death was assessed by Fluoro-Jade C staining. We report that low concentrations of Aβ(25-35) increased hemichannel activity in all three cell types and microglia initiate these effects triggered by Aβ. Finally, neuronal damage occurs by activation of neuronal hemichannels induced by ATP and glutamate released from Aβ(25-35)-activated glia. These responses were observed in the presence of external calcium and were differently inhibited by hemichannel blockers, whereas the Aβ(25-35)-induced neuronal damage was importantly reduced in acute slices made from Cx43 knock-out mice. Thus, Aβ leads to a cascade of hemichannel activation in which microglia promote the release of glutamate and ATP through glial (microglia and astrocytes) hemichannels that induces neuronal death by triggering hemichannels in neurons. Consequently, this work opens novel avenues for alternative treatments that target glial cells and neurons to maintain neuronal survival in the presence of Aβ.

The impact-parameter dependent saturation model (IP-Sat) is a simple dipole model that incorporates key features of the physics of gluon saturation and matches smoothly to the perturbative QCD dipole expression at large ${Q}^{2}$ for a given $x$. It was previously shown that the model gives a good description of HERA data suggesting evidence for gluon saturation effects at small $x$. The model has also been applied to proton-proton and proton-nucleus collisions and provides the basis for the IP-Glasma model of initial conditions in heavy ion collisions. Here we present a reanalysis of available data in electron-proton collisions at small Bjorken $x$, including the recently released combined data from the ZEUS and H1 collaborations. We first confront the model to the high precision combined data for the reduced cross section and obtain its parameters. With these parameters fixed, we compare model results to the data for the structure function ${F}_{2}$, the longitudinal structure function ${F}_{L}$, the charm structure function ${F}_{2}^{c\overline{c}}$, exclusive vector meson ($J/\ensuremath{\psi}$, $\ensuremath{\phi}$ and $\ensuremath{\rho}$) production, and deeply virtual Compton scattering. Excellent agreement is obtained for the processes considered at small $x$ in a wide range of ${Q}^{2}$. Our results strongly hint at universality of the IP-Sat dipole amplitude and the extracted impact-parameter distribution of the proton. They also provide a benchmark for further refinements in studies of QCD saturation at colliders.

Recent in vitro evidence indicates that astrocytes can modulate synaptic plasticity by releasing neuroactive substances (gliotransmitters). However, whether gliotransmitter release from astrocytes is necessary for higher brain function in vivo , particularly for memory, as well as the contribution of connexin (Cx) hemichannels to gliotransmitter release, remain elusive. Here, we microinfused into the rat basolateral amygdala (BLA) TAT‐Cx43L2, a peptide that selectively inhibits Cx43‐hemichannel opening while maintaining synaptic transmission or interastrocyte gap junctional communication. In vivo blockade of Cx43 hemichannels during memory consolidation induced amnesia for auditory fear conditioning, as assessed 24 h after training, without affecting short‐term memory, locomotion, or shock reactivity. The amnesic effect was transitory, specific for memory consolidation, and was confirmed after microinfusion of Gap27, another Cx43‐hemichannel blocker. Learning capacity was recovered after coinfusion of TAT‐Cx43L2 and a mixture of putative gliotransmitters (glutamate, glutamine, lactate, d ‐serine, glycine, and ATP). We propose that gliotransmitter release from astrocytes through Cx43 hemichannels is necessary for fear memory consolidation at the BLA. Thus, the present study is the first to demonstrate a physiological role for astroglial Cx43 hemichannels in brain function, making these channels a novel pharmacological target for the treatment of psychiatric disorders, including post‐traumatic stress disorder.—Stehberg, J., Moraga‐Amaro, R., Salazar, C., Becerra, A., Echeverría, C., Orellana, J. A., Bultynck, G., Ponsaerts, R., Leybaert, L., Simon, F., Sáez, J. C., Retamal, M. A. Release of gliotransmitters through astroglial connexin 43 hemichannels is necessary for fear memory consolidation in the basolateral amygdala. FASEB J. 26, 3649–3657 (2012). www.fasebj.org

Using nonlinear evolution equations of QCD, we compute the von Neumann entropy of the system of partons resolved by deep inelastic scattering at a given Bjorken $x$ and momentum transfer ${q}^{2}=\ensuremath{-}{Q}^{2}$. We interpret the result as the entropy of entanglement between the spatial region probed by deep inelastic scattering and the rest of the proton. At small $x$ the relation between the entanglement entropy $S(x)$ and the parton distribution $xG(x)$ becomes very simple: $S(x)=\mathrm{ln}[xG(x)]$. In this small $x$, large rapidity $Y$ regime, all partonic microstates have equal probabilities---the proton is composed by an exponentially large number $\mathrm{exp}(\mathrm{\ensuremath{\Delta}}Y)$ of microstates that occur with equal and exponentially small probabilities $\mathrm{exp}(\ensuremath{-}\mathrm{\ensuremath{\Delta}}Y)$, where $\mathrm{\ensuremath{\Delta}}$ is defined by $xG(x)\ensuremath{\sim}1/{x}^{\mathrm{\ensuremath{\Delta}}}$. For this equipartitioned state, the entanglement entropy is maximal---so at small $x$, deep inelastic scattering probes a maximally entangled state. We propose the entanglement entropy as an observable that can be studied in deep inelastic scattering. This will require event-by-event measurements of hadronic final states, and would allow to study the transformation of entanglement entropy into the Boltzmann one. We estimate that the proton is represented by the maximally entangled state at $x\ensuremath{\le}{10}^{\ensuremath{-}3}$; this kinematic region will be amenable to studies at the Electron Ion Collider.

The impact-parameter dependent color glass condensate (b-CGC) dipole model is based on the Balitsky-Kovchegov nonlinear evolution equation and improves the Iancu-Itakura-Munier dipole model by incorporating the impact-parameter dependence of the saturation scale. Here we confront the model to the recently released high precision combined Hadron Electron Ring Accelerator (HERA) data and obtain its parameters. The b-CGC results are then compared to data at small $x$ for the structure function, the longitudinal structure function, the charm structure function, exclusive vector meson ($J/\ensuremath{\psi}$, $\ensuremath{\phi}$, and $\ensuremath{\rho}$) production and deeply virtual Compton scattering. We also compare our results with the impact-parameter dependent saturation (IP-Sat) model. We show that most features of inclusive deep inelastic scattering and exclusive diffractive data, including the ${Q}^{2}$, $W$, $|t|$, and $x$ dependence, are correctly reproduced in both models. Nevertheless, the b-CGC and the impact-parameter dependent saturation (IP-Sat) models give different predictions beyond the current HERA kinematics, namely for the structure functions at very low $x$ and high virtualities ${Q}^{2}$, and for the exclusive diffractive vector meson and deeply virtual Compton scattering production at high $t$. This can be traced back to the different power-law behavior of the saturation scale in $x$ and to a different impact-parameter $b$ dependence of the saturation scale in these models. Nevertheless, both models give approximately similar saturation scales ${Q}_{S}<1\text{ }\text{ }\mathrm{GeV}$ for the proton in HERA kinematics, and also both models lead to the same conclusion that the typical impact parameter probed in the total ${\ensuremath{\gamma}}^{*}p$ cross section is about $b\ensuremath{\approx}2--3\text{ }\text{ }{\mathrm{GeV}}^{\ensuremath{-}1}$. Our results provide a benchmark for further investigation of QCD at small $x$ in heavy ion collisions at RHIC and the LHC and also at future experiments such as an electron-ion collider and the LHeC.

Odontoblasts are dentin-secreting cells that survive for the whole life of a healthy tooth. Once teeth are completely erupted, odontoblasts transform into a mature stage that allows for their functional conservation for decades, while maintaining the capacity for secondary and reactionary dentin secretion. Odontoblasts are also critically involved in the transmission of sensory stimuli from the dentin-pulp complex and in the cellular defense against pathogens. Their longevity is sustained by an elaborate autophagic-lysosomal system that ensures organelle and protein renewal. However, progressive dysfunction of this system, in part caused by lipofuscin accumulation, reduces the fitness of odontoblasts and eventually impairs their dentin maintenance capacity. Here we review the functional activities assumed by mature odontoblasts throughout life. Understanding the biological basis of age-related changes in human odontoblasts is crucial to improving tooth preservation in the elderly.

We study the mass spectrum and decay constants of light and heavy mesons in a soft-wall holographic approach, using the correspondence of string theory in Anti-de Sitter space and conformal field theory in physical space-time.

We discuss a holographic soft-wall model developed for the description of mesons and baryons with adjustable quantum numbers $n$, $J$, $L$, $S$. This approach is based on an action which describes hadrons with broken conformal invariance and which incorporates confinement through the presence of a background dilaton field. We show that in the case of the bound-state problem (hadronic mass spectrum) two versions of the model with a positive and negative dilaton profile are equivalent to each other by a special transformation of the bulk field. We also comment on recent works which discuss the dilaton sign in the context of soft-wall approaches.

Sterile neutrinos with masses in the range of 1--100 GeV have been searched for in a variety of experiments. Here, we discuss the prospects of searching for sterile neutrinos at the LHC using displaced vertices. Two different cases are discussed: (i) the standard model extended with sterile neutrinos, and (ii) right-handed neutrinos in a left-right symmetric extension of the standard model. A dedicated displaced vertex search will allow us to probe parts of the parameter space not accessible to other searches, but both cases will require a large luminosity.

We systematically study exclusiv2 diffractive (photo)production of vector mesons ($J/\ensuremath{\psi}$, $\ensuremath{\psi}(2s)$, $\ensuremath{\phi}$, and $\ensuremath{\rho}$) off protons in high-energy collisions and investigate whether the production is a sensitive probe of gluon saturation. We confront saturation-based results for diffractive $\ensuremath{\psi}(2s)$ and $\ensuremath{\rho}$ production at HERA and $J/\ensuremath{\psi}$ photoproduction with all available data, including recent work from HERA, ALICE, and LHCb, finding good agreement. In particular, we show that the $t$ distribution of differential cross sections of photoproduction of vector mesons offers a unique opportunity to discriminate among saturation and nonsaturation models. This is due to the emergence of a pronounced dip (or multiple dips) in the $t$ distribution of diffractive photoproduction of vector mesons at relatively large, but potentially accessible $|t|$ that can be traced back to the unitarity features of color dipole amplitude in the saturation regime. We show that in saturation models the dips in $t$ distribution recede towards lower $|t|$ with decreasing mass of the vector meson, increasing energy or decreasing Bjorken-$x$, and decreasing virtuality $Q$. We provide various predictions for exclusive (photo)production of different vector mesons including the ratio of $\ensuremath{\psi}(2s)/J/\ensuremath{\psi}$ at HERA, the LHC, and future colliders.

A bstract Heavy Neutral Leptons (HNLs) are hypothetical particles predicted by many extensions of the Standard Model. These particles can, among other things, explain the origin of neutrino masses, generate the observed matter-antimatter asymmetry in the Universe and provide a dark matter candidate. The SHiP experiment will be able to search for HNLs produced in decays of heavy mesons and travelling distances ranging between $$ \mathcal{O} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>O</mml:mi> </mml:math> (50 m) and tens of kilometers before decaying. We present the sensitivity of the SHiP experiment to a number of HNL’s benchmark models and provide a way to calculate the SHiP’s sensitivity to HNLs for arbitrary patterns of flavour mixings. The corresponding tools and data files are also made publicly available.

In this paper, model-predictive control is used as a framework for implementing a quasi-time-optimal speed controller for a permanent-magnet synchronous motor. The scheme consists of an inner predictive torque control, which makes use of the full actuation range provided by a two-level voltage source inverter, although with the use of pulsewidth modulation. An outer speed controller, based on classical results for the time-optimal control of the double integrator, constitutes a good example application of the proposed torque controller. The overall scheme achieves both fast transient dynamics (as fast as the physics of the system and the control constraints allow) and acceptable steady-state performance.

A bstract Long-lived light particles (LLLPs) appear in many extensions of the standard model. LLLPs are usually motivated by the observed small neutrino masses, by dark matter or both. Typical examples for fermionic LLLPs (a.k.a. heavy neutral fermions, HNFs) are sterile neutrinos or the lightest neutralino in R-parity violating supersymmetry. The high luminosity LHC is expected to deliver up to 3/ab of data. Searches for LLLPs in dedicated experiments at the LHC could then probe the parameter space of LLLP models with unprecedented sensitivity. Here, we compare the prospects of several recent experimental proposals, FASER, CODEX-b and MATHUSLA, to search for HNFs and discuss their relative merits.s

In a previous publication, we have presented a model for the photoproduction of $J/\ensuremath{\psi}$ vector mesons off protons, where the proton structure in the impact-parameter plane is described by an energy-dependent hot-spot profile. Here we extend this model to study the photonuclear production of $J/\ensuremath{\psi}$ vector mesons in coherent and incoherent interactions of heavy nuclei. We study two methods to extend the model to the nuclear case: using the standard Glauber-Gribov formalism and using geometric scaling to obtain the nuclear saturation scale. We find that the incoherent cross section changes sizably with the inclusion of subnucleonic hot spots and that this change is energy dependent. We propose to search for this behavior by measuring the ratio of the incoherent to coherent cross sections at different energies. We compare the results of our model to results from the Relativistic Heavy-Ion Collider (RHIC) and from run 1 at the Large Hadron Collider (LHC), finding satisfactory agreement. We also present predictions for the LHC at the new energies reached in run 2. The predictions include $J/\ensuremath{\psi}$ production in ultraperipheral collisions, as well as the recently observed photonuclear production in peripheral collisions.

Abstract Historical records of an earthquake that occurred in 1730 affecting Metropolitan Chile provide essential clues on the source characteristics for the future earthquakes in the region. The earthquake and tsunami of 1730 have been recognized as the largest to occur in Metropolitan Chile since the beginning of written history. The earthquake destroyed buildings along &gt;1000 km of the coast and produced a large tsunami that caused damage as far as Japan. Here its source characteristics are inferred by comparing local tsunami inundations computed from hypothetical earthquakes with varying magnitude and depth, with those inferred from historical observations. It is found that a 600–800 km long rupture involving average slip amounts of 10–14 m ( M w 9.1–9.3) best explains the observed tsunami heights and inundations. This large earthquake magnitude is supported by the 1730 tsunami heights inferred in Japan. The inundation results combined with local uplift reports suggest a southward increase of the slip depth along the rupture zone of the 1730 earthquake. While shallow slip on the area to the north of the 2010 earthquake rupture zone is required to explain the reported inundation, only deeper slip at this area can explain the coastal uplift reports. Since the later earthquakes of the region involved little or no slip at shallow depths, the near‐future earthquakes on Metropolitan Chile could release the shallow slip accumulated since 1730 and thus lead to strong tsunami excitation. Moderate shaking from a shallow earthquake could delay tsunami evacuation for the most populated coastal region of Chile.

We revisit the mechanism of neutrinoless double beta ($0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$) decay mediated by the exchange with the heavy Majorana neutrino $N$ of arbitrary mass ${m}_{N}$, slightly mixed $\ensuremath{\sim}{U}_{\mathit{eN}}$ with the electron neutrino ${\ensuremath{\nu}}_{e}$. By assuming the dominance of this mechanism, we update the well-known $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$-decay exclusion plot in the ${m}_{N}\ensuremath{-}{U}_{\mathit{eN}}$ plane taking into account recent progress in the calculation of nuclear matrix elements within quasiparticle random phase approximation and improved experimental bounds on the $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$-decay half-life of $^{76}\mathrm{Ge}$ and $^{136}\mathrm{Xe}$. We also consider the known formula approximating the ${m}_{N}$ dependence of the $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$-decay nuclear matrix element in a simple explicit form. We analyze its accuracy and specify the corresponding parameters, allowing one to easily calculate the $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$-decay half-life for arbitrary ${m}_{N}$ for all the experimentally interesting isotopes without resorting to real nuclear structure calculations.