A CT-based revised description and phylogenetic analysis of the skull of the basal maniraptoran Ornitholestes hermanni Osborn 1903

Ornitholestes hermanni was one of the first small-bodiedtheropods named in the 1900s. It is known from a singlespecimen discovered during the American MuseumExpedition of 1900, at the Jurassic Morrison Formationsite known as Bone Cabin Quarry, in Wyoming. It haslong been a critical taxon in understanding the evolutionof the Coelurosauria, the clade that includestyrannosauroids, living birds, and their commonancestors. The holotype specimen comprises a nearlycomplete skull and most of a postcranial skeleton. Despitethis abundant material, its precise phylogeneticrelationships have been difficult to determine. This is inpart due to the intense mediolateral crushing of the skulland the relatively generalized postcranial anatomy. Herewe present the results of a micro- computed tomographybasedinvestigation of the cranial anatomy and subsequentincorporation of these data into a phylogenetic data matrixdesigned to test coelurosaurian interrelationships. We findrobust evidence across different optimality criteria thatOrnitholestes is the earliest-branching oviraptorosaurianspecies. Using parsimony as an optimality criterion, thisphylogenetic position is supported by 14 unambiguoussynapomorphies, including: a short frontal process of thepostorbital; short, deep, and pendant paroccipitalprocesses; a large mandibular foramen; an anterodorsallyoriented dentary symphysis; a surangular that is longerthan the dentary; short maxillary and dentary tooth rows;and procumbent dentary and premaxillary teeth. UsingBayesian fossilized birth-death models, we find highposterior probabilities (>.99) that Ornitholestes is theearliest-branching oviraptorosaurian species. Weadditionally find strong support in both analyses that thesuperficially bat-like and possibly arborealscansoriopterygids are an early branching lineage withinOviraptorosauria. This new phylogenetic position fills in apersistent ghost lineage in Oviraptorosauria and confirmsthat scansoriopterygids are basally branchingoviraptorosaurians that represent an independent origin ofaerial habits, separate from those of dromaeosaurs andavialans.Fil: Chapelle, Kimberley E.. American Museum of Natural History; Estados UnidosFil: Norell, Mark. American Museum of Natural History; Estados UnidosFil: Ford, David P.. University of the Witwatersrand; SudáfricaFil: Hendrickx, Christophe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; ArgentinaFil: Radermacher, Viktor J.. University of Minnesota; Estados UnidosFil: Balanoff, Amy. University Johns Hopkins; Estados UnidosFil: Zanno, Lindsay E.. North Carolina Museum of Natural Sciences; Estados UnidosFil: Choiniere, Jonah N.. University of the Witwatersrand; Sudáfrica81st Annual Meeting of the Society of Vertebrate PaleontologyMc LeanEstados UnidosSociety of Vertebrate Paleontolog

Deep evolutionary diversification of semicircular canals in archosaurs

Living archosaurs (birds and crocodylians) have disparate locomotor strategies that evolved since their divergence ∼250 mya. Little is known about the early evolution of the sensory structures that are coupled with these changes, mostly due to limited sampling of early fossils on key stem lineages. In particular, the morphology of the semicircular canals (SCCs) of the endosseous labyrinth has a long-hypothesized relationship with locomotion. Here, we analyze SCC shapes and sizes of living and extinct archosaurs encompassing diverse locomotor habits, including bipedal, semi-aquatic, and flying taxa. We test form-function hypotheses of the SCCs and chronicle their evolution during deep archosaurian divergences. We find that SCC shape is statistically associated with both flight and bipedalism. However, this shape variation is small and is more likely explained by changes in braincase geometry than by locomotor changes. We demonstrate high disparity of both shape and size among stem-archosaurs and a deep divergence of SCC morphologies at the bird-crocodylian split. Stem-crocodylians exhibit diverse morphologies, including aspects also present in birds and distinct from other reptiles. Therefore, extant crocodylian SCC morphologies do not reflect retention of a ?primitive? reptilian condition. Key aspects of bird SCC morphology that hitherto were interpreted as flight related, including large SCC size and enhanced sensitivity, appeared early on the bird stem-lineage in non-flying dinosaur precursors. Taken together, our results indicate a deep divergence of SCC traits at the bird?crocodylian split and that living archosaurs evolved from an early radiation with high sensory diversity.Fil: Bronzati Filho, Mario. Universidade de Sao Paulo; BrasilFil: Benson, Roger B. J.. University of Oxford; Reino UnidoFil: Evers, Serjoscha W.. University of Oxford; Reino UnidoFil: Ezcurra, Martin Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Cabreira, Sergio F.. No especifíca;Fil: Choiniere, Jonah. University of the Witwatersrand; SudáfricaFil: Dollman, Kathleen N.. University of the Witwatersrand; SudáfricaFil: Paulina Carabajal, Ariana. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche; ArgentinaFil: Radermacher, Viktor J.. University of the Witwatersrand; SudáfricaFil: Roberto da Silva, Lucio. No especifíca;Fil: Sobral, Gabriela. Staatliches Museum Für Naturkunde Stuttgart; AlemaniaFil: Stocker, Michelle R.. No especifíca;Fil: Witmer, Lawrence. No especifíca;Fil: Langer, Max C.. Universidade de Sao Paulo; BrasilFil: Nesbitt, Sterling J.. No especifíca

Search for high-mass exclusive γγ\gamma\gamma→\to WW and γγ\gamma\gamma→\to ZZ production in proton-proton collisions at s\sqrt{s} = 13 TeV

A search is performed for exclusive high-mass $\gamma\gamma$$\to$ WW and $\gamma\gamma$$\to$ ZZ production in proton-proton collisions using intact forward protons reconstructed in near-beam detectors, with both weak bosons decaying into boosted and merged jets. The analysis is based on a sample of proton-proton collisions collected by the CMS and TOTEM experiments at $\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 100 fb$^{−1}$. No excess above the standard model background prediction is observed, and upper limits are set on the pp → pWWp and pp → pZZp cross sections in a fiducial region defined by the diboson invariant mass m(VV) > 1 TeV (with V = W, Z) and proton fractional momentum loss 0.04 < $ξ$ < 0.20. The results are interpreted as new limits on dimension-6 and dimension-8 anomalous quartic gauge couplings.[graphic not available: see fulltext

Measurement of pseudorapidity distributions of charged particles in proton-proton collisions at sqrt(s) = 8 TeV by the CMS and TOTEM experiments

Pseudorapidity ( $\eta$ ) distributions of charged particles produced in proton–proton collisions at a centre-of-mass energy of 8 $~\text {TeV}$ are measured in the ranges $|\eta | < 2.2$ and $5.3 < |\eta | < 6.4$ covered by the CMS and TOTEM detectors, respectively. The data correspond to an integrated luminosity of $\mathcal {L} = 45 \mu {\mathrm {b}}^{-1}$ . Measurements are presented for three event categories. The most inclusive category is sensitive to 91–96 % of the total inelastic proton–proton cross section. The other two categories are disjoint subsets of the inclusive sample that are either enhanced or depleted in single diffractive dissociation events. The data are compared to models used to describe high-energy hadronic interactions. None of the models considered provide a consistent description of the measured distributions

First search for exclusive diphoton production at high mass with tagged protons in proton-proton collisions at s=\sqrt{s} = 13 TeV

A search for exclusive two-photon production via photon exchange in proton-proton collisions, pp $\to$ p$\gamma\gamma$p with intact protons, is presented. The data correspond to an integrated luminosity of 9.4 fb$^{-1}$ collected in 2016 using the CMS and TOTEM detectors at a center-of-mass energy of 13 TeV at the LHC. Events are selected with a diphoton invariant mass above 350 GeV and with both protons intact in the final state, to reduce backgrounds from strong interactions. The events of interest are those where the invariant mass and rapidity calculated from the momentum losses of the forward-moving protons matches the mass and rapidity of the central, two-photon system. No events are found that satisfy this condition. Interpreting this result in an effective dimension-8 extension of the standard model, the first limits are set on the two anomalous four-photon coupling parameters. If the other parameter is constrained to its standard model value, the limits at 95% CL are $\lvert\zeta_1\rvert$ $\lt$ 2.9 $\times$ 10$^{-13}$ GeV$^{-4}$ and $\lvert\zeta_2\rvert$ $\lt$ 6.0 $\times$ 10$^{-13}$ GeV$^{-4}$

Hard color-singlet exchange in dijet events in proton-proton collisions at s=\sqrt{s} = 13 TeV

International audienceEvents where the two leading jets are separated by a pseudorapidity interval devoid of particle activity, known as jet-gap-jet events, are studied in proton-proton collisions at $\sqrt{s} =$ 13 TeV. The signature is expected from hard color-singlet exchange. Each of the highest transverse momentum ($p_\mathrm{T}$) jets must have $p_\mathrm{T}^\text{jet}$$\gt$ 40 GeV and pseudorapidity 1.4 $\lt$$|\eta^\text{jet}|$$\lt$ 4.7, with $\eta^\text{jet1} \eta^\text{jet2}$$\lt$ 0, where $\text{jet1}$ and $\text{jet2}$ are the leading and subleading jets in $p_\mathrm{T}$, respectively. The analysis is based on data collected by the CMS and TOTEM experiments during a low luminosity, high-$\beta^*$ run at the CERN LHC in 2015, with an integrated luminosity of 0.66 pb$^{-1}$. Events with a low number of charged particles with $p_\mathrm{T}$$\gt$ 0.2 GeV in the interval $|\eta|$$\lt$ 1 between the jets are observed in excess of calculations that assume only color-exchange. The fraction of events produced via color-singlet exchange, $f_\text{CSE}$, is measured as a function of $p_\mathrm{T}^\text{jet2}$, the pseudorapidity difference between the two leading jets, and the azimuthal angular separation between the two leading jets. The fraction $f_\text{CSE}$ has values of 0.4-1.0%. The results are compared with previous measurements and with predictions from perturbative quantum chromodynamics. In addition, the first study of jet-gap-jet events detected in association with an intact proton using a subsample of events with an integrated luminosity of 0.40 pb$^{-1}$ is presented. The intact protons are detected with the Roman pot detectors of the TOTEM experiment. The $f_\text{CSE}$ in this sample is 2.91 $\pm$ 0.70 (stat) $^{+1.08}_{-1.01}$ (syst) times larger than that for inclusive dijet production in dijets with similar kinematics

First search for exclusive diphoton production at high mass with tagged protons in proton-proton collisions at s=\sqrt{s} = 13 TeV

International audienceA search for exclusive two-photon production via photon exchange in proton-proton collisions, pp $\to$ p$\gamma\gamma$p with intact protons, is presented. The data correspond to an integrated luminosity of 9.4 fb$^{-1}$ collected in 2016 using the CMS and TOTEM detectors at a center-of-mass energy of 13 TeV at the LHC. Events are selected with a diphoton invariant mass above 350 GeV and with both protons intact in the final state, to reduce backgrounds from strong interactions. The events of interest are those where the invariant mass and rapidity calculated from the momentum losses of the forward-moving protons matches the mass and rapidity of the central, two-photon system. No events are found that satisfy this condition. Interpreting this result in an effective dimension-8 extension of the standard model, the first limits are set on the two anomalous four-photon coupling parameters. If the other parameter is constrained to its standard model value, the limits at 95% CL are $\lvert\zeta_1\rvert$ $\lt$ 2.9 $\times$ 10$^{-13}$ GeV$^{-4}$ and $\lvert\zeta_2\rvert$ $\lt$ 6.0 $\times$ 10$^{-13}$ GeV$^{-4}$

First search for exclusive diphoton production at high mass with tagged protons in proton-proton collisions at s\sqrt{s} = 13 TeV

A search for exclusive two-photon production via photon exchange in proton-proton collisions, pp $\to$ p$\gamma\gamma$p with intact protons, is presented. The data correspond to an integrated luminosity of 9.4 fb$^{-1}$ collected in 2016 using the CMS and TOTEM detectors at a center-of-mass energy of 13 TeV at the LHC. Events are selected with a diphoton invariant mass above 350 GeV and with both protons intact in the final state, to reduce backgrounds from strong interactions. The events of interest are those where the invariant mass and rapidity calculated from the momentum losses of the forward-moving protons matches the mass and rapidity of the central, two-photon system. No events are found that satisfy this condition. Interpreting this result in an effective dimension-8 extension of the standard model, the first limits are set on the two anomalous four-photon coupling parameters. If the other parameter is constrained to its standard model value, the limits at 95% CL are $\lvert\zeta_1\rvert\lt$ 2.88$\times$10$^{-13}$ GeV$^{-4}$ and $\lvert\zeta_2\rvert\lt$6.02$\times$10$^{-13}$GeV$^{-4}$

Measurement of single-diffractive dijet production in proton-proton collisions at s=\sqrt{s} =s​= 8 TeV with the CMS and TOTEM experiments

Measurements are presented of the single-diffractive dijet cross section and the diffractive cross section as a function of the proton fractional momentum loss $\xi$ and the four-momentum transfer squared t. Both processes ${\text{ p }{}{}} {\text{ p }{}{}} \rightarrow {\text{ p }{}{}} {\text{ X }}$ and ${\text{ p }{}{}} {\text{ p }{}{}} \rightarrow {\text{ X }} {\text{ p }{}{}}$, i.e. with the proton scattering to either side of the interaction point, are measured, where ${\text{ X }}$ includes at least two jets; the results of the two processes are averaged. The analyses are based on data collected simultaneously with the CMS and TOTEM detectors at the LHC in proton–proton collisions at $\sqrt{s} = 8\,\text {Te}\text {V}$ during a dedicated run with $\beta ^{*} = 90\,\text {m}$ at low instantaneous luminosity and correspond to an integrated luminosity of $37.5{\,\text {nb}^{-1}}$. The single-diffractive dijet cross section $\sigma ^{{\text{ p }{}{}} {\text{ X }}}_{\mathrm {jj}}$, in the kinematic region $\xi 40\,\text {Ge}\text {V}$, and pseudorapidity $|\eta | < 4.4$, is 21.7 \pm 0.9\,\text {(stat)} \,^{+3.0}_{-3.3}\,\text {(syst)} \pm 0.9\,\text {(lumi)} \,\text {nb} . The ratio of the single-diffractive to inclusive dijet yields, normalised per unit of $\xi$, is presented as a function of x, the longitudinal momentum fraction of the proton carried by the struck parton. The ratio in the kinematic region defined above, for x values in the range $-2.9 \le \log _{10} x \le -1.6$, is $R = (\sigma ^{{\text{ p }{}{}} {\text{ X }}}_{\mathrm {jj}}/\Delta \xi )/\sigma _{\mathrm {jj}} = 0.025 \pm 0.001\,\text {(stat)} \pm 0.003\,\text {(syst)}$, where $\sigma ^{{\text{ p }{}{}} {\text{ X }}}_{\mathrm {jj}}$ and $\sigma _{\mathrm {jj}}$ are the single-diffractive and inclusive dijet cross sections, respectively. The results are compared with predictions from models of diffractive and nondiffractive interactions. Monte Carlo predictions based on the HERA diffractive parton distribution functions agree well with the data when corrected for the effect of soft rescattering between the spectator partons