LIP - AP - Física de Partículas e Astropartículas
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- Vector Boson Scattering Processes: Status and ProspectsPublication . Diogo Buarque Franzosi; Michele Gallinaro; Richard Ruiz; Thea K. Aarrestad; Flavia Cetorelli; Mauro Chiesa; Antonio Costantini; Ansgar Denner; Stefan Dittmaier; Robert Franken; Pietro Govoni; Tao Han; Ashutosh V. Kotwal; Jinmian Li; Kristin Lohwasser; Kenneth Long; Yang Ma; Luca Mantani; Matteo Marchegiani; Mathieu Pellen; Giovanni Pelliccioli; Karolos Potamianos; Jürgen Reuter; Timo Schmidt; Christopher Schwan; Michał Szleper; Rob Verheyen; Keping Xie; Rao ZhangInsight into the electroweak (EW) and Higgs sectors can be achieved through measurements of vector boson scattering (VBS) processes. The scattering of EW bosons are rare processes that are precisely predicted in the Standard Model (SM) and are closely related to the Higgs mechanism. Modifications to VBS processes are also predicted in models of physics beyond the SM (BSM), for example through changes to the Higgs boson couplings to gauge bosons and the resonant production of new particles. In this review, experimental results and theoretical developments of VBS at the Large Hadron Collider, its high luminosity upgrade, and future colliders are presented.
- Sensitivity of the SHiP experiment to light dark matterPublication . Ahdida, C.; Akmete, A.; Albanese, R.; Alexandrov, A.; Anokhina, A.; Aoki, S.; Arduini, G.; Atkin, E.; Azorskiy, N.; Back, J. J.; Bagulya, A.; Karpenkov, D.; Kershaw, K.; Battistin, M.; Uvarov, L.; Khabibullin, M.; Bezshyiko, I.; Golubkov, D.; Khalikov, E.; Khaustov, G.; Tosi, N.; D’Appollonio, G.; Krasilnikova, I.; Khoriauli, G.; Redi, F.; Khotyantsev, A.; Sanchez Galan, F.; Durhan, O.; Kim, Y. G.; Lantwin, O.; Vankova-Kirilova, G.; Marsh, S.; de Asmundis, R.; Kolev, D. I.; Marshall, A. M.; Mattelaer, O.; Mefodev, A.; Mermod, P.; Miano, A.; Mikado, S.; Mikhaylov, Yu.; Milstead, D. A.; Poliakov, V.; De Carvalho Saraiva, J.; Rodin, Volodymyr; Pastore, A.; Di Giulio, L.; Sato, O.; Prieto Prieto, J.; Ehlert, M.; Mineev, O.; Robbe, P.; Froeschl, R.; Montanari, A.; Rademakers, A.; Berdnikov, Y. A.; Bondarenko, K.; Woo, J.-K.; Montesi, M. C.; Morishima, K.; Rovelli, T.; Movchan, S.; Yoon, C. S.; Bencivenni, G.; Muttoni, Y.; De Lellis, G.; Naganawa, N.; Elikkaya, E.; Nakamura, M.; Tramontano, F.; Fabbri, F.; Bieschke, S.; Bonivento, W. M.; Nakano, T.; Di Marco, N.; Nasybulin, S.; Kono, A.; Frugiuele, C.; Ninin, P.; Venturi, V.; Gatignon, L.; Ferrillo, M.; Nishio, A.; Polukhina, N.; Bertani, M.; Novikov, A.; Enik, T.; Bick, D.; Obinyakov, B.; Kurochka, V.; Ogawa, S.; Okateva, N.; Wurm, M.; Treille, D.; Savchenko, E. S.; Golovtsov, V.; Kitagawa, N.; Opitz, B.; de Magistris, M.; Rodin, Viktor; Osborne, J.; Ovchynnikov, M.; Fukuda, T.; Dib, C.; Owtscharenko, N.; Golovatiuk, A.; Malinin, A.; Owen, P. H.; Pacholek, P.; De Roeck, A.; Ratnikov, F.; Betancourt, C.; Vilchinski, S.; Paoloni, A.; Xella, S.; Korol’ko, I.; Park, B. D.; Rodrigues Cavalcante, A. B.; Dijkstra, H.; Schliwinski, J. S.; Petridis, K.; Schmidt-Parzefall, W.; Serra, N.; Sgobba, S.; Shadura, O.; Shakin, A.; Shaposhnikov, M.; Shatalov, P.; Shchedrina, T.; Tsenov, R.; Vincke, Helmut; Than Naing, S.; Ko, J.-W.; Zaytsev, Yu.; Ulin, S.; Korzenev, A.; Blanco, A.; Vlasik, K.; Lauria, A.; Shchutska, L.; Baaltasar Dos Santos, F.; Baranov, A.; Fedin, O.; Shevchenko, V.; Shibuya, H.; Wertelaers, P.; Shirobokov, S.; Filippov, K.; Gavrilov, G.; Shustov, A.; Silverstein, S. B.; Bay, A.; Simone, S.; De Serio, M.; Kovalenko, S.; Golutvin, A.; Gorshenkov, M.; Simoniello, R.; Kodama, K.; Skorokhvatov, M.; Lee, K. S.; Smirnov, S.; Dougherty, L. A.; Lopes, L.; Kurbatov, P.; Boehm, J.; Boiarska, I.; Goddard, B.; Sohn, J. Y.; Kostyukhin, V.; Sokolenko, A.; Ricciardi, S.; Solodko, E.; Starkov, N.; Fedotovs, F.; De Simone, D.; Zelenov, A.; Maleev, V.; Patel, M.; Stoel, L.; Visone, C.; Stramaglia, M. E.; Sukhonos, D.; Lee, K. Y.; Bauche, J.; Suzuki, Y.; Magnan, A.; Sanz Ull, A.; Takahashi, S.; Tastet, J. L.; Vannucci, F.; Golinka-Bezshyyko, L.; Dolmatov, A.; Bogomilov, M.; Felici, G.; Prokudin, M.; Teterin, P.; Volkov, A.; Kolesnikov, A.; Zimmerman, J.; Borburgh, J.; Boyarsky, A.; Brenner, R.; Breton, D.; Büscher, V.; Buonaura, A.; Buonocore, L.; Buontempo, S.; Dedenko, L.; Donskov, S.; Pereyma, D.; Fini, R. A.; Dergachev, P.; Prota, A.; Gorbounov, P.; Dubreuil, A.; Roganova, T.; Cadeddu, S.; Fraser, M.; Fresa, R.; Calcaterra, A.; Calviani, M.; Etenko, A.; Campanelli, M.; Kuznetsova, E.; Lopez Sola, E.; Casolino, M.; Charitonidis, N.; Gall, J.; Chau, P.; Rakai, A.; Maltoni, F.; Berdnikov, A. Y.; Chauveau, J.; Perillo-Marcone, A.; Chepurnov, A.; Rokujo, H.; Chernyavskiy, M.; Kolosov, V.; Ruchayskiy, O.; Gorbunov, D.; Gorkavenko, V.; Lyubovitskij, V.; Choi, K.-Y.; Quercia, A.; Chumakov, A.; Vincke, Heinz; Ciambrone, P.; Cicero, V.; Kudenko, Y.; Fonte, P.; Santos Diaz, P.; Timiryasov, I.; Congedo, L.; Drohan, V.; Cornelis, K.; Cristinziani, M.; Rosa, G.; Galati, G.; Crupano, A.; Yilmazer, A. U.; Dallavalle, G. M.; Datwyler, A.; Dmitrenko, V.; Maalmi, J.; Komatsu, M.; Gorbunov, S.; Kurbatov, E.; Ursov, E.; D’Ambrosio, N.; Petkov, G. L.; Franco, C.; Grachev, V.; Grandchamp, A. L.; Graverini, E.; Grenard, J.-L.; Grenier, D.; Grichine, V.; Gruzinskii, N.; Guler, A. M.; Konovalova, N.; Tioukov, V.; Lacker, H. M.; Kim, V.; Ustyuzhanin, A.; Manabe, Y.; Korol, I.; Voronkov, R.; Guz, Yu.; Lanfranchi, G.; Bardou, F.; Haefeli, G. J.; Koukovini Platia, E.; Hagner, C.; Rinaldesi, M.; Ruf, T.; Hakobyan, H.; Harris, I. W.; Loschiavo, V. P.; van Herwijnen, E.; Saputi, A.; Gentile, V.; Hessler, C.; Tommasini, D.; Hollnagel, A.; van Waasen, S.; Hosseini, B.; Petrov, A.; Williams, O.; Managadze, A. K.; Samoylenko, V.; Hushchyn, M.; Uteshev, Z.; Iaselli, G.; Domenici, D.; Barker, G. J.; Iuliano, A.; Rawlings, T.; Bayliss, V.; Yilmaz, D.; Jacobsson, R.; Kormannshaus, S.; Joković, D.; Jonker, M.; Wanke, R.; Lévy, J.-M.; Kadenko, I.; Ferro-Luzzi, M.; Kain, V.; Kaiser, B.; Samsonov, V.; Podgrudkov, D.; Manfredi, M.; Bezshyyko, O.; Di Crescenzo, A.; Kamiscioglu, C.; Torii, M.; Lamont, M.Dark matter is a well-established theoretical addition to the Standard Model supported by many observations in modern astrophysics and cosmology. In this context, the existence of weakly interacting massive particles represents an appealing solution to the observed thermal relic in the Universe. Indeed, a large experimental campaign is ongoing for the detection of such particles in the sub-GeV mass range. Adopting the benchmark scenario for light dark matter particles produced in the decay of a dark photon, with αD = 0.1 and mA′ = 3mχ, we study the potential of the SHiP experiment to detect such elusive particles through its Scattering and Neutrino detector (SND). In its 5-years run, corresponding to 2 · 1020 protons on target from the CERN SPS, we find that SHiP will improve the current limits in the mass range for the dark matter from about 1 MeV to 300 MeV. In particular, we show that SHiP will probe the thermal target for Majorana candidates in most of this mass window and even reach the Pseudo-Dirac thermal relic.
- Search for large missing transverse momentum in association with one top-quark in proton-proton collisions at $\sqrt{s}=13$ TeV with the ATLAS detectorPublication . ATLAS CollaborationThis paper describes a search for events with one top-quark and large missing transverse momentum in the final state. Data collected during 2015 and 2016 by the ATLAS experiment from 13 TeV proton-proton collisions at the LHC corresponding to an integrated luminosity of 36.1 fb$^{-1}$ are used. Two channels are considered, depending on the leptonic or the hadronic decays of the $W$ boson from the top quark. The obtained results are interpreted in the context of simplified models for dark-matter production and for the single production of a vector-like $T$ quark. In the absence of significant deviations from the Standard Model background expectation, 95% confidence-level upper limits on the corresponding production cross-sections are obtained and these limits are translated into constraints on the parameter space of the models considered.
- A Simultaneous Description of Hadron and Jet Suppression in Heavy Ion CollisionsPublication . Jorge Casalderrey-Solana; Zachary Hulcher; Guilherme Milhano; Daniel Pablos; Krishna RajagopalWe present a global fit to all data on the suppression of high energy jets and high energy hadrons in the most central heavy ion collisions at the LHC for two different collision energies, within a hybrid strong/weak coupling quenching model. Even though the measured suppression factors for hadrons and jets differ significantly from one another and appear to asymptote to different values in the high energy limit, we obtain a simultaneous description of all these data after constraining the value of a single model parameter. We use our model to investigate the origin of the difference between the observed suppression of jets and hadrons and relate it, quantitatively, to the observed modification of the jet fragmentation function in jets that have been modified by passage through the medium produced in heavy ion collisions. In particular, the observed increase in the fraction of hard fragments in medium-modified jets, which indicates that jets with the fewest hardest fragments lose the least energy, corresponds quantitatively to the observed difference between the suppression of hadrons and jets. We argue that a harder fragmentation pattern for jets with a given energy after quenching is a generic feature of any mechanism for the interaction between jets and the medium that they traverse that yields a larger suppression for wider jets. We also compare the results of our global fit to LHC data to measurements of the suppression of high energy hadrons in RHIC collisions, and find that with its parameter chosen to fit the LHC data our model is inconsistent with the RHIC data at the $3\sigma$ level, suggesting that hard probes interact more strongly with the less hot quark-gluon plasma produced at RHIC.
- Constraints on mediator-based dark matter and scalar dark energy models using $\sqrt s = 13$ TeV $pp$ collision data collected by the ATLAS detectorPublication . ATLAS CollaborationConstraints on selected mediator-based dark matter models and a scalar dark energy model using up to $37~\mathrm{fb}^{-1}$ $\sqrt s = 13$ TeV $pp$ collision data collected by the ATLAS detector at the LHC during 2015-2016 are summarised in this paper. The results of experimental searches in a variety of final states are interpreted in terms of a set of spin-1 and spin-0 single-mediator dark matter simplified models and a second set of models involving an extended Higgs sector plus an additional vector or pseudo-scalar mediator. The searches considered in this paper constrain spin-1 leptophobic and leptophilic mediators, spin-0 colour-neutral and colour-charged mediators and vector or pseudo-scalar mediators embedded in extended Higgs sector models. In this case, also $\sqrt s = 8$ TeV $pp$ collision data are used for the interpretation of the results. The results are also interpreted for the first time in terms of light scalar particles that could contribute to the accelerating expansion of the universe (dark energy).
- NRQCD colour-octet expansion vs. LHC quarkonium production: signs of a hierarchy puzzle?Publication . Faccioli, Pietro; Lourenço, Carlos
- Sorting out quenched jetsPublication . Jasmine Brewer; José Guilherme Milhano; Jesse ThalerWe introduce a new 'quantile' analysis strategy to study the modification of jets as they traverse through a droplet of quark-gluon plasma. To date, most jet modification studies have been based on comparing the jet properties measured in heavy-ion collisions to a proton-proton baseline at the same reconstructed jet transverse momentum ($p_T$). It is well known, however, that the quenching of jets from their interaction with the medium leads to a migration of jets from higher to lower $p_T$, making it challenging to directly infer the degree and mechanism of jet energy loss. Our proposed quantile matching procedure is inspired by (but not reliant on) the approximate monotonicity of energy loss in the jet $p_T$. In this strategy, jets in heavy-ion collisions ordered by $p_T$ are viewed as modified versions of the same number of highest-energy jets in proton-proton collisions, and the fractional energy loss as a function of jet $p_T$ is a natural observable ($Q_{\rm AA}$). Furthermore, despite non-monotonic fluctuations in the energy loss, we use an event generator to validate the strong correlation between the $p_T$ of the parton that initiates a heavy-ion jet and the $p_T$ of the vacuum jet which corresponds to it via the quantile procedure ($p_T^{\rm quant}$). We demonstrate that this strategy both provides a complementary way to study jet modification and mitigates the effect of $p_T$ migration in heavy-ion collisions.
- Transverse Extension of Partons in the Proton probed by Deeply Virtual Compton ScatteringPublication . R. Akhunzyanov; M. G. Alexeev; G. D. Alexeev; A. Amoroso; V. Andrieux; N. V. Anfimov; V. Anosov; A. Antoshkin; K. Augsten; W. Augustyniak; A. Austregesilo; C. D. R. Azevedo; B. Badelek; F. Balestra; M. Ball; J. Barth; R. Beck; Y. Bedfer; J. Bernhard; K. Bicker; E. R. Bielert; R. Birsa; M. Bodlak; P. Bordalo; F. Bradamante; A. Bressan; M. Buechele; E. Burtin; V. E. Burtsev; W. -C. Chang; C. Chatterjee; M. Chiosso; I. Choi; A. G. Chumakov; S. -U. Chung; A. Cicuttin; M. L. Crespo; S. Dalla Torre; S. S. Dasgupta; S. Dasgupta; O. Yu. Denisov; L. Dhara; S. V. Donskov; N. Doshita; Ch. Dreisbach; W. Duennweber; R. R. Dusaev; M. Dziewiecki; A. Efremov; P. D. Eversheim; M. Faessler; A. Ferrero; M. Finger; M. Finger jr.; H. Fischer; C. Franco; N. du Fresne von Hohenesche; J. M. Friedrich; V. Frolov; E. Fuchey; F. Gautheron; O. P. Gavrichtchouk; S. Gerassimov; J. Giarra; I. Gnesi; M. Gorzellik; A. Grasso; A. Gridin; M. Grosse Perdekamp; B. Grube; T. Grussenmeyer; A. Guskov; D. Hahne; G. Hamar; D. von Harrach; R. Heitz; F. Herrmann; N. Horikawa; N. d'Hose; C. -Y. Hsieh; S. Huber; S. Ishimoto; A. Ivanov; Yu. Ivanshin; T. Iwata; V. Jary; R. Joosten; P. Joerg; K. Juraskova; E. Kabuss; A. Kerbizi; B. Ketzer; G. V. Khaustov; Yu. A. Khokhlov; Yu. Kisselev; F. Klein; J. H. Koivuniemi; V. N. Kolosov; K. Kondo; I. Konorov; V. F. Konstantinov; A. M. Kotzinian; O. M. Kouznetsov; Z. Kral; M. Kraemer; F. Krinner; Z. V. Kroumchtein; Y. Kulinich; F. Kunne; K. Kurek; R. P. Kurjata; I. I. Kuznetsov; A. Kveton; A. A. Lednev; E. A. Levchenko; M. Levillain; S. Levorato; Y. -S. Lian; J. Lichtenstadt; R. Longo; V. E. Lyubovitskij; A. Maggiora; A. Magnon; N. Makins; N. Makke; G. K. Mallot; S. A. Mamon; C. Marchand; B. Marianski; A. Martin; J. Marzec; J. Matousek; H. Matsuda; T. Matsuda; G. V. Meshcheryakov; M. Meyer; W. Meyer; Yu. V. Mikhailov; M. Mikhasenko; E. Mitrofanov; N. Mitrofanov; Y. Miyachi; A. Moretti; A. Nagaytsev; F. Nerling; D. Neyret; J. Novy; W. -D. Nowak; G. Nukazuka; A. S. Nunes; A. G. Olshevsky; I. Orlov; M. Ostrick; D. Panzieri; B. Parsamyan; S. Paul; J. -C. Peng; F. Pereira; G. Pesaro; M. Pesek; M. Peskova; D. V. Peshekhonov; N. Pierre; S. Platchkov; J. Pochodzalla; V. A. Polyakov; J. Pretz; M. Quaresma; C. Quintans; S. Ramos; C. Regali; G. Reicherz; C. Riedl; N. S. Rogacheva; D. I. Ryabchikov; A. Rybnikov; A. Rychter; R. Salac; V. D. Samoylenko; A. Sandacz; C. Santos; S. Sarkar; I. A. Savin; T. Sawada; G. Sbrizzai; P. Schiavon; H. Schmieden; K. Schoennig; E. Seder; A. Selyunin; L. Silva; L. Sinha; S. Sirtl; M. Slunecka; J. Smolik; A. Srnka; D. Steffen; M. Stolarski; O. Subrt; M. Sulc; H. Suzuki; A. Szabelski; T. Szameitat; P. Sznajder; M. Tasevsky; S. Tessaro; F. Tessarotto; A. Thiel; J. Tomsa; F. Tosello; V. Tskhay; S. Uhl; B. I. Vasilishin; A. Vauth; B. M. Veit; J. Veloso; A. Vidon; M. Virius; S. Wallner; M. Wilfert; J. ter Wolbeek; K. Zaremba; P. Zavada; M. Zavertyaev; E. Zemlyanichkina; N. Zhuravlev; M. ZiembickiWe report on the first measurement of exclusive single-photon muoproduction on the proton by COMPASS using 160 GeV/$c$ polarized $\mu^+$ and $\mu^-$ beams of the CERN SPS impinging on a liquid hydrogen target. We determine the dependence of the average of the measured $\mu^+$ and $\mu^-$ cross sections for deeply virtual Compton scattering on the squared four-momentum transfer $t$ from the initial to the final final proton. The slope $B$ of the $t$-dependence is fitted with a single exponential function, which yields $B=(4.3 \ \pm \ 0.6_{\text{stat}}\_{- \ 0.3}^{+ \ 0.1}\big\rvert_{\text{sys}}) (\text{GeV}/c)^{-2}$. This result can be converted into an average transverse extension of partons in the proton, $\sqrt{\langle r_{\perp}^2 \rangle} = (0.58 \ \pm \ 0.04_{\text{stat}}\_{- \ 0.02}^{+ \ 0.01}\big\rvert_{\text{sys}})\text{fm}$. For this measurement, the average virtuality of the photon mediating the interaction is $\langle Q^2 \rangle = 1.8\,(\text{GeV/}c)^2$ and the average value of the Bjorken variable is $\langle x_{\text{Bj}} \rangle = 0.056$.
- Top Quark Anomalous Couplings at the High-Luminosity Phase of the LHCPublication . Frédéric Déliot; Miguel C. N. Fiolhais; António OnofreThe combination of the latest and most precise measurements of several top quark properties is presented in this paper in order to establish allowed regions on anomalous contributions to the Lorentz structure of the $Wtb$ vertex. These measurements include single top production cross sections, $W$ boson helicity fractions and forward-backward asymmetries, both at Tevatron and at the Large Hadron Collider, up to a center-of-mass energy of 13 TeV. The results obtained at 95% Confidence Level for the top quark anomalous couplings are compared with the limits extracted from a combination that includes the expected measurements at the future High-Luminosity run of the Large Hadron Collider.
- Numerical modeling of cosmic-ray transport in the heliosphere and interpretation of the proton-to-helium ratio in Solar Cycle 24Publication . Nicola Tomassetti; Fernando Barão; Bruna Bertucci; Emanuele Fiandrini; Miguel OrcinhaThanks to space-borne experiments of cosmic-ray (CR) detection, such as the AMS and PAMELA missions in low-Earth orbit, or the Voyager-1 spacecraft in the interstellar space, a large collection of multi-channel and time-resolved CR data has become available. Recently, the AMS experiment has released new precision data, on the proton and helium fluxes in CRs, measured on monthly basis during its first six years of mission. The AMS data reveal a remarkable long-term behavior in the temporal evolution of the proton-to-helium ratio at rigidity $R = p/Z <$ 3 GV. As we have argued in a recent work, such a behavior may reflect the transport properties of low-rigidity CRs in the inteplanetary space. In particular, it can be caused by mass/charge dependence of the CR diffusion coefficient. In this paper, we present our developments in the numerical modeling of CR transport in the Milky Way and in the heliosphere. Within our model, and with the help of approximated analytical solutions, we describe in details the relations between the properties of CR diffusion and the time-dependent evolution of the proton-to-helium ratio.