Ref HAL: hal-01099930_v1
Ref Arxiv: 1412.8182
DOI: 10.1007/JHEP02(2015)176
WoS: 000350695900001
Ref. & Cit.: NASA ADS
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13 Citations
Résumé:

We use the twistorial construction of D-instantons in Calabi-Yau compactifications of type II string theory to compute an explicit expression for the metric on the hypermultiplet moduli space affected by these non-perturbative corrections. In this way we obtain an exact quaternion-Kahler metric which is a non-trivial deformation of the local c-map. In the four-dimensional case corresponding to the universal hypermultiplet, our metric fits the Tod ansatz and provides an exact solution of the continuous Toda equation. We also analyze the fate of the curvature singularity of the perturbative metric by deriving an S-duality invariant equation which determines the singularity hypersurface after inclusion of the D(-1)-instanton effects.

Commentaires: 20+12+4 pages

Ref HAL: hal-01060212_v1
PMID 25983647
Ref Arxiv: 1409.0659
DOI: 10.1140/epjc/s10052-014-3252-1
WoS: WOS:000348993400003
Ref. & Cit.: NASA ADS
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40 Citations
Résumé:

We show that novel paths to dark matter generation and baryogenesis are open when the Standard Model is extended with three sterile neutrinos $N_i$ and a charged scalar $\delta^+$. Specifically, we propose a new production mechanism for the dark matter particle --a multi-keV sterile neutrino, $N_1$-- that does not depend on the active-sterile mixing angle and does not rely on a large primordial lepton asymmetry. Instead, $N_1$ is produced, via freeze-in, by the decays of $\delta^+$ while it is in equilibrium in the early Universe. In addition, we demonstrate that, thanks to the couplings between the heavier sterile neutrinos $N_{2,3}$ and $\delta^+$, baryogenesis via leptogenesis can be realized close to the electroweak scale. The lepton asymmetry is generated either by $N_{2,3}$-decays for masses $M_{2,3}\gtrsim$ TeV, or by $N_{2,3}$-oscillations for $M_{2,3}\sim$ GeV. Experimental signatures of this scenario include an X-ray line from dark matter decays, and the direct production of $\delta^+$ at the LHC. This model thus describes a minimal, testable scenario for neutrino masses, the baryon asymmetry, and dark matter.

Commentaires: 15 pages

Ref Arxiv: 1408.4674
DOI: 10.1140/epjc/s10052-014-3231-6
WoS: 000348992600002
Ref. & Cit.: NASA ADS
32 Citations
Résumé:

A measurement of $\textit{W}$ boson production in lead-lead collisions at $\sqrt{s_{\mathrm{NN}}}=$2.76 TeV is presented. It is based on the analysis of data collected with the ATLAS detector at the LHC in 2011 corresponding to an integrated luminosity of 0.14 $\mathrm{nb}^{-1}$ and 0.15 $\mathrm{nb}^{-1}$ in the muon and electron decay channels, respectively. The differential production cross-sections and lepton charge asymmetry are each measured as a function of the average number of participating nucleons $\langle N_{\mathrm{part}} \rangle$ and absolute pseudorapidity of the charged lepton. The results are compared to predictions based on next-to-leading-order QCD calculations. These measurements are, in principle, sensitive to possible nuclear modifications to the parton distribution functions and also provide information on scaling of $\textit{W}$ boson production in multi-nucleon systems.

Commentaires: See paper for full list of authors - 18 pages plus author list + cover pages (33 pages total), 11 figures, 5 tables, submitted to EPJC, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2013-05/

PMID 26709345
Ref Arxiv: 1406.0076
DOI: 10.1140/epjc/s10052-014-3190-y
WoS: 000348991900001
Ref. & Cit.: NASA ADS
222 Citations
Résumé:

The jet energy scale (JES) and its systematic uncertainty are determined for jets measured with the ATLAS detector using proton-proton collision data with a centre-of-mass energy of $\sqrt{s}=7$ TeV corresponding to an integrated luminosity of 4.7 fb$^{-1}$. Jets are reconstructed from energy deposits forming topological clusters of calorimeter cells using the anti-k$_t$ algorithm with distance parameters $R=0.4$ or $R=0.6$, and are calibrated using MC simulations. A residual JES correction is applied to account for differences between data and MC simulations. This correction and its systematic uncertainty are estimated using a combination of in situ techniques exploiting the transverse momentum balance between a jet and a reference object such as a photon or a Z boson, for $20 < p_t < 1000$ GeV and pseudorapidities $|\eta|<4.5$. The effect of multiple proton-proton interactions is corrected for, and an uncertainty is evaluatedusing in situ techniques. The smallest JES uncertainty of less than $1 \%$ is found in the central calorimeter region($|\eta|<1.2$) for jets with $55< p_t< 500$ GeV. For central jets at lower $p_t$, the uncertainty is about $3 \%$. A consistent JES estimate is found using measurements of the calorimeter response of single hadrons in proton-proton collisionsand test-beam data, which also provide the estimate for $p_{t,jet} > 1$ TeV. The calibration of forward jets is derived from dijet $p_t$ balance measurements. The resulting uncertainty reaches its largest value of $6\%$ for low-$p_t$ jets at $|\eta|=4.5$. Additional JES uncertainties due to specific event topologies, such as close-by jets or selections of event samples with an enhanced content of jets originating from light quarks or gluons, are also discussed. The magnitude of these uncertainties depends on the event sample used in a given physics analysis, but typically amounts to $0.5\%$ to $3\%$.

Commentaires: See paper for full list of authors - 88 pages plus author list + cover pages (101 pages total), 66 figures, 14 tables, submitted to European Physics Journal C, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/PERF-2012-14/PERF-2012-01

Ref Arxiv: 1406.5053
DOI: 10.1103/PhysRevLett.114.081802
WoS: 000350210600004
Ref. & Cit.: NASA ADS
38 Citations
Résumé:

Searches are performed for resonant and non-resonant Higgs boson pair production in the hh to gamma gamma b bbar final state using 20 fb-1 of proton--proton collisions at a center-of-mass energy of 8 TeV recorded with the ATLAS detector at the CERN Large Hadron Collider. A 95% confidence level upper limit on the cross section times branching ratio of non-resonant production is set at 2.2 pb, while the expected limit is 1.0 pb. The corresponding limit observed for a narrow resonance ranges between 0.8 and 3.5 pb as a function of its mass.

Commentaires: See paper for full list of authors - 6 pages plus author list (19 pages total), 3 figures, 0 tables, submitted to Physical Review Letters, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HIGG-2013-29/

Ref Arxiv: 1407.0573
DOI: 10.1103/PhysRevD.91.052005
WoS: 000351283000001
Ref. & Cit.: NASA ADS
7 Citations
Résumé:

Simultaneous measurements of the $t\bar{t}$, $W^+W^-$, and $Z/\gamma^{*}\rightarrow\tau\tau$ production cross-sections using an integrated luminosity of 4.6 fb$^{-1}$ of $pp$ collisions at $\sqrt{s} = 7$ TeV collected by the ATLAS detector at the LHC are presented. Events are selected with two high transverse momentum leptons consisting of an oppositely charged electron and muon pair. The three processes are separated using the distributions of the missing transverse momentum of events with zero and greater than zero jet multiplicities. Measurements of the fiducial cross-section are presented along with results that quantify for the first time the underlying correlations in the predicted and measured cross-sections due to proton parton distribution functions. These results indicate that the correlated NLO predictions for $t\bar{t}$ and $Z/\gamma^{*}\rightarrow\tau\tau$ significantly underestimate the data, while those at NNLO generally describe the data well. The full cross-sections are measured to be $\sigma(t\bar{t}) = 181.2 \pm 2.8^{+9.7}_{-9.5} \pm 3.3 \pm 3.3 $ pb, $\sigma(W^+W^-) = 53.3 \pm 2.7^{+7.3}_{-8.0} \pm 1.0 \pm 0.5$ pb, and $\sigma(Z/\gamma^{*}\rightarrow\tau\tau) = 1174 \pm 24^{+72}_{-87} \pm 21 \pm 9$ pb, where the cited uncertainties are due to statistics, systematic effects, luminosity and the LHC beam energy measurement, respectively.

Commentaires: See paper for full list of authors - 22 pages plus author list + cover pages (35 pages total), 7 figures, 7 tables, submitted to PRD, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2012-05/

Ref HAL: hal-00808906_v1
Ref Arxiv: 1304.0766
DOI: 10.1090/pspum/090/01523
WoS: WOS:000376419100009
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15 Citations
Résumé:

The hypermultiplet moduli space M_H in type II string theories compactified on a Calabi-Yau threefold X is largely constrained by supersymmetry (which demands quaternion-Kählerity), S-duality (which requires an isometric action of SL(2, Z)) and regularity. Mathematically, M_H ought to encode all generalized Donaldson-Thomas invariants on X consistently with wall-crossing, modularity and homological mirror symmetry. We review recent progress towards computing the exact metric on M_H, or rather the exact complex contact structure on its twistor space.

Commentaires: 31 pages; Contribution to the Proceedings of String Math 2012