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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fassi, F., Ferrer, A., et al. (2013). Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC. Phys. Lett. B, 726(1-3), 88–119.
Abstract: Measurements are presented of production properties and couplings of the recently discovered Higgs boson using the decays into boson pairs, H -> gamma gamma, H -> ZZ* -> 4l and H -> WW* -> l nu l nu. The results are based on the complete pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at centre-of-mass energies of root s = 7 TeV and root s = 8 TeV, corresponding to an integrated luminosity of about 25 fb(-1). Evidence for Higgs boson production through vector-boson fusion is reported. Results of combined fits probing Higgs boson couplings to fermions and bosons, as well as anomalous contributions to loop-induced production and decay modes, are presented. All measurements are consistent with expectations for the Standard Model Higgs boson.
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fassi, F., Ferrer, A., et al. (2013). Evidence for the spin-0 nature of the Higgs boson using ATLAS data. Phys. Lett. B, 726(1-3), 120–144.
Abstract: Studies of the spin and parity quantum numbers of the Higgs boson are presented, based on protonproton collision data collected by the ATLAS experiment at the LHC. The Standard Model spin-parity J(P) = 0(+) hypothesis is compared with alternative hypotheses using the Higgs boson decays H -> gamma gamma, H -> ZZ* -> 4l and H -> WW* -> l nu l nu, as well as the combination of these channels. The analysed dataset corresponds to an integrated luminosity of 20.7 fb(-1) collected at a centre-of-mass energy of root s = 8 TeV. For the H -> ZZ* -> 4l decay mode the dataset corresponding to an integrated luminosity of 4.6 fb(-1) collected at root s = 7 TeV is included. The data are compatible with the Standard Model J(P) = 0+ quantum numbers for the Higgs boson, whereas all alternative hypotheses studied in this Letter, namely some specific J(P) = 0(-), 1(+), 1(-), 2(+) models, are excluded at confidence levels above 97.8%. This exclusion holds independently of the assumptions on the coupling strengths to the Standard Model particles and in the case of the J(P) = 2(+) model, of the relative fractions of gluon-fusion and quark-antiquark production of the spin-2 particle. The data thus provide evidence for the spin-0 nature of the Higgs boson, with positive parity being strongly preferred.
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Scandale, W. et al, & Lari, L. (2013). Optimization of the crystal assisted collimation of the SPS beam. Phys. Lett. B, 726(1-3), 182–186.
Abstract: The possibility for optimization of crystal assisted collimation has been studied at the CERN SPS for stored beams of protons and Pb ions with 270 GeV/c per unit charge. A bent silicon crystal used as a primary collimator deflects halo particles in the channeling regime, directing them into a tungsten absorber. In channeling conditions a strong reduction of off-momentum particle numbers produced in the crystal and absorber, which form collimation leakage, has been observed in the first high dispersion (HD) area downstream. The present study shows that the collimation leakage is minimal for some values of the absorber offset relative to the crystal. The optimal offset value is larger for Pb ions because of their considerably larger ionization losses in the crystal, which cause large increases of particle betatron oscillation amplitudes. The optimal absorber offset allows obtaining maximal efficiency of crystal-assisted collimation.
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Stanja, J. et al, Agramunt, J., & Algora, A. (2013). Mass spectrometry and decay spectroscopy of isomers across the Z=82 shell closure. Phys. Rev. C, 88(5), 054304–7pp.
Abstract: Recent results from a measurement campaign studying the isomerism in neutron-deficient Tl isotopes are presented. The measurements make use of a nuclear spectroscopy setup coupled to the high-resolution Penningtrap mass spectrometer ISOLTRAP at CERN's radioactive ion-beam facility ISOLDE. The mass values of Tl-190,Tl-194 are improved and a mass-spin-state assignment is carried out. An additional mass measurement of the grandparent nuclide At-198 allows the deduction of the spin-state ordering in Tl-190. As a result, the excitation energies of the isomers in both Tl isotopes are determined for the first time to Eex(Tl-194) = 260(15) keV and E-ex(Tl-190) = 89(12) keV. Furthermore, this allows anchoring of the ground-state and isomer masses of Bi-194, Fr-202, and Ac-206, which are linked by two independent a-decay chains.
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Mantovani-Sarti, V., Park, B. Y., & Vento, V. (2013). The Soliton-Soliton Interaction in the Chiral Dilaton Model. Int. J. Mod. Phys. A, 28(27), 1350136–19pp.
Abstract: We study the interaction between two B = 1 states in the Chiral Dilaton Model where baryons are described as nontopological solitons arising from the interaction of chiral mesons and quarks. By using the hedgehog solution for B = 1 states we construct, via a product ansatz, three possible B = 2 configurations to analyse the role of the relative orientation of the hedgehog quills in the dynamics of the soliton-soliton interaction and investigate the behavior of these solutions in the range of long/intermediate distance. One of the solutions is quite binding due to the dynamics of the pi and sigma fields at intermediate distance and should be used for nuclear matter studies. Since the product ansatz break down as the two solitons get close, we explore the short range distance regime with a model that describes the interaction via a six-quark bag ansatz. We calculate the interaction energy as a function of the inter-soliton distance and show that for small separations the six quarks bag, assuming a hedgehog structure, provides a stable bound state that at large separations connects with a special configuration coming from the product ansatz.
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NEXT Collaboration(Alvarez, V. et al), Carcel, S., Cervera-Villanueva, A., Diaz, J., Ferrario, P., Gil, A., et al. (2013). Operation and first results of the NEXT-DEMO prototype using a silicon photomultiplier tracking array. J. Instrum., 8, P09011–20pp.
Abstract: NEXT-DEMO is a high-pressure xenon gas TPC which acts as a technological test-bed and demonstrator for the NEXT-100 neutrinoless double beta decay experiment. In its current configuration the apparatus fully implements the NEXT-100 design concept. This is an asymmetric TPC, with an energy plane made of photomultipliers and a tracking plane made of silicon photomultipliers (SiPM) coated with TPB. The detector in this new configuration has been used to reconstruct the characteristic signature of electrons in dense gas, demonstrating the ability to identify the MIP and “blob” regions. Moreover, the SiPM tracking plane allows for the definition of a large fiducial region in which an excellent energy resolution of 1.82% FWHM at 511 keV has been measured (a value which extrapolates to 0.83% at the xenon Q(beta beta)).
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Mateu, V., & Rodrigo, G. (2013). Oriented event shapes at (NLL)-L-3 + O(alpha(2)(S)). J. High Energy Phys., 11(11), 030–29pp.
Abstract: We analyze oriented event-shapes in the context of Soft-Collinear Effective Theory (SCET) and in fixed-order perturbation theory. Oriented event-shapes are distributions of event-shape variables which are differential on the angle theta(T) that the thrust axis forms with the electron-positron beam. We show that at any order in perturbation theory and for any event shape, only two angular structures can appear: F-0 = 3/8 (1+cos(2) theta(T)) and F-1 = (1 – 3 cos(2) theta(T)). When integrating over theta(T) to recover the more familiar event-shape distributions, only F-0 survives. The validity of our proof goes beyond perturbation theory, and hence only these two structures are present at the hadron level. The proof also carries over massive particles. Using SCET techniques we show that singular terms can only arise in the F-0 term. Since only the hard function is sensitive to the orientation of the thrust axis, this statement applies also for recoil-sensitive variables such as Jet Broadening. We show how to carry out resummation of the singular terms at (NLL)-L-3 for Thrust, Heavy-Jet Mass, the sum of the Hemisphere Masses and C-parameter by using existing computations in SCET. We also compute the fixed-order distributions for these event-shapes at O(alpha(S)) analytically and at O(alpha(2)(S)) with the program Event2.
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ATLAS Collaboration(Aad, G. et al), Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Fassi, F., Ferrer, A., et al. (2013). Measurement of the top quark charge in pp collisions at root s=7 TeV with the ATLAS detector. J. High Energy Phys., 11(11), 031–42pp.
Abstract: A measurement of the top quark electric charge is carried out in the ATLAS experiment at the Large Hadron Collider using 2.05 fb(-1) of data at a centre-of-mass energy of 7TeV. In units of the elementary electric charge, the top quark charge is determined to be 0.64 +/- 0.02 (stat.) +/- 0.08 (syst.) from the charges of the top quark decay products in single lepton t (t) over bar candidate events. This excludes models that propose a heavy quark of electric charge -4/3, instead of the Standard Model top quark, with a significance of more than 8 sigma.
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Barenboim, G., Bosch, C., Lopez-Ibañez, M. L., & Vives, O. (2013). Eviction of a 125 GeV “heavy”-Higgs from the MSSM. J. High Energy Phys., 11(11), 051–39pp.
Abstract: We prove that the present experimental constraints are already enough to rule out the possibility of the similar to 125 GeV Higgs found at LHC being the second lightest Higgs in a general MSSM context, even with explicit CP violation in the Higgs potential. Contrary to previous studies, we are able to eliminate this possibility analytically, using simple expressions for a relatively small number of observables. We show that the present LHC constraints on the diphoton signal strength, tau tau production through Higgs and BR(B -> X-s gamma) are enough to preclude the possibility of H-2 being the observed Higgs with m(H) similar or equal to 125 GeV within an MSSM context, without leaving room for finely tuned cancellations. As a by-product, we also comment on the difficulties of an MSSM interpretation of the excess in the gamma gamma production cross section recently found at CMS that could correspond to a second Higgs resonance at m(H) similar or equal to 136 GeV.
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Xiao, C. W., & Oset, E. (2013). Hidden beauty baryon states in the local hidden gauge approach with heavy quark spin symmetry. Eur. Phys. J. A, 49(11), 139–12pp.
Abstract: Using a coupled-channel unitary approach, combining the heavy quark spin symmetry and the dynamics of the local hidden gauge, we investigate the meson-baryon interaction with hidden beauty and obtain several new states of N around 11 GeV. We consider the basis of states eta (b) N, I'N, BI > (b) , BI pound (b) , B (*) I > (b) , B (*) I pound (b) , B (*) I pound (b) (*) and find four basic bound states which correspond to BI pound (b) , BI pound (b) (*) , B (*) I pound (b) and B (*) I pound (b) (*) , decaying mostly into eta (b) N and I'N and with a binding energy about 50-130 MeV with respect to the thresholds of the corresponding channel. All of them have isospin I = 1/2 , and we find no bound states or resonances in I = 3/2 . The BI pound (b) state appears in J = 1/2 , the BI pound (b) (*) in J = 3/2 , the B (*) I pound (b) appears nearly degenerate in J = 1/2 , 3/2 and the B (*) I pound (b) (*) appears nearly degenerate in J = 1/2 , 3/2, 5/2. These states have a width from 2-110 MeV, with conservative estimates of uncertainties, except for the one in J = 5/2 which has zero width since it cannot decay into any of the states of the basis chosen. We make generous estimates of the uncertainties and find that within very large margins these states appear bound.
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