CERN Accelerating science

TH Articles

Ultimi arrivi:
2015-03-13
07:51
Addressing the LHC flavour anomalies with horizontal gauge symmetries / Crivellin, Andreas (CERN) ; D'Ambrosio, Giancarlo (CERN ; INFN, Naples) ; Heeck, Julian (Brussels U.)
We study the impact of an additional $U(1)'$ gauge symmetry with flavour-dependent charges for quarks and leptons on the LHC flavour anomalies observed in $B \to K^* \mu^+\mu^-$, $R(K) = B \to K \mu^+\mu^-/B \to K e^+e^-$, and $h \to \mu\tau$. In its minimal version with two scalar doublets, the resulting model naturally explains the deviations from the Standard Model observed in $B \to K^* \mu^+\mu^-$ and $R(K)$. [...]
arXiv:1503.03477; CERN-PH-TH-2015-046; ULB-TH-15-03.- 2015 - 14 p. - Published in : Phys. Rev. D 91 (2015) 075006 Fulltext: PDF; External link: Preprint

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2015-01-07
09:01
Explaining $h\to\mu^\pm\tau^\mp$, $B\to K^* \mu^+\mu^-$ and $B\to K \mu^+\mu^-/B\to K e^+e^-$ in a two-Higgs-doublet model with gauged $L_\mu-L_\tau$ / Crivellin, Andreas (CERN) ; D'Ambrosio, Giancarlo (CERN ; INFN, Naples) ; Heeck, Julian (Brussels U.)
The LHC observed so far three deviations from the Standard Model (SM) predictions in flavour observables: LHCb reported anomalies in $B\to K^* \mu^+\mu^-$ and $R(K)=B\to K \mu^+\mu^-/B\to K e^+e^-$ while CMS found an excess in $h\to\mu\tau$. We show, for the first time, how these deviations from the SM can be explained within a single well-motivated model: a two-Higgs-doublet model with gauged $L_\mu-L_\tau$ symmetry. [...]
arXiv:1501.00993; CERN-PH-TH-2015-001; ULB-TH-14-26.- 2015 - 6 p. - Published in : Phys. Rev. Lett. 114 (2015) 151801 Fulltext: PDF; External link: Preprint

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2014-12-12
08:08
Hamiltonian truncation study of the $\phi ^{4}$ theory in two dimensions / Rychkov, Slava (CERN ; Paris U., VI-VII ; Ecole Normale Superieure) ; Vitale, Lorenzo G (IPT, Lausanne)
We defend the Fock-space Hamiltonian truncation method, which allows to calculate numerically the spectrum of strongly coupled quantum field theories, by putting them in a finite volume and imposing a UV cutoff. The accuracy of the method is improved via an analytic renormalization procedure inspired by the usual effective field theory. [...]
arXiv:1412.3460; CERN-PH-TH-2014-254.- 2015 - 39 p. - Published in : Phys. Rev. D 91 (2015) 085011 Fulltext: PDF; External link: Preprint

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2014-12-04
08:01
Flipped GUT Inflation / Ellis, John (King's Coll. London ; CERN) ; Gonzalo, Tomas E (University Coll. London) ; Harz, Julia (University Coll. London) ; Huang, Wei-Chih (University Coll. London)
We analyse the prospects for constructing hybrid models of inflation that provide a dynamical realisation of the apparent closeness between the supersymmetric GUT scale and the possible scale of cosmological inflation. In the first place, we consider models based on the flipped SU(5)$\times$U(1) gauge group, which has no magnetic monopoles. [...]
arXiv:1412.1460; KCL-PH-TH-2014-49; LCTS-2014-50; CERN-PH-TH-2014-241.- 2015 - 20 p. - Published in : J. Cosmol. Astropart. Phys. 03 (2015) 039 Fulltext: PDF; External link: Preprint

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2014-11-25
12:23
New Higgs Inflation in a No-Scale Supersymmetric SU(5) GUT / Ellis, John (Trinity Coll., Dublin ; CERN) ; He, Hong-Jian (Tsinghua U., Beijing, CHEP ; Peking U., CHEP) ; Xianyu, Zhong-Zhi (Tsinghua U., Beijing, CHEP ; Peking U., CHEP)
Higgs inflation is attractive because it identifies the inflaton with the electroweak Higgs boson. In this work, we construct a new class of supersymmetric Higgs inflationary models in the no-scale supergravity with an SU(5) GUT group. [...]
arXiv:1411.5537; KCL-PH-TH-2014-48; LCTS-2014-49; CERN-PH-TH-2014-230.- 2015 - Published in : Phys. Rev. D 91 (2015) 021302 Fulltext: PDF; External link: Preprint

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2014-11-19
09:34
On the two-loop corrections to the Higgs masses in the NMSSM / Goodsell, Mark D (Paris U., VI-VII ; Paris, LPTHE) ; Nickel, Kilian (Bonn U.) ; Staub, Florian (CERN)
We discuss the impact of the two-loop corrections to the Higgs mass in the NMSSM beyond $O(\alpha_S(\alpha_b + \alpha_t))$. For this purpose we use the combination of the public tools SARAH and SPheno to include all contributions stemming from superpotential parameters. [...]
arXiv:1411.4665; BONN-TH-2014-16; CERN-PH-TH-2014-231.- 2015 - 23 p. - Published in : Phys. Rev. D 91 (2015) 035021 Fulltext: PDF; External link: Preprint

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2014-11-13
07:52
Nonlinear evolution of density and flow perturbations on a Bjorken background / Brouzakis, Nikolaos (Athens U.) ; Floerchinger, Stefan (CERN) ; Tetradis, Nikolaos (Athens U. ; CERN) ; Wiedemann, Urs Achim (CERN)
Density perturbations and their dynamic evolution from early to late times can be used for an improved understanding of interesting physical phenomena both in cosmology and in the context of heavy-ion collisions. We discuss the spectrum and bispectrum of these perturbations around a longitudinally expanding fireball after a heavy-ion collision. [...]
arXiv:1411.2912; CERN-PH-TH-2014-223.- 2015 - 30 p. - Published in : Phys. Rev. D 91 (2015) 065007 Fulltext: PDF; External link: Preprint

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2014-11-13
07:49
Accelerating cosmological expansion from shear and bulk viscosity / Floerchinger, Stefan (CERN) ; Tetradis, Nikolaos (Athens U. ; CERN) ; Wiedemann, Urs Achim (CERN)
The dissipation of energy from local velocity perturbations in the cosmological fluid affects the time evolution of spatially averaged fluid dynamic fields and the cosmological solution of Einstein's field equations. We show how this backreaction effect depends on shear and bulk viscosity and other material properties of the dark sector, as well as the spectrum of perturbations. [...]
arXiv:1411.3280; CERN-PH-TH-2014-224.- 2015 - 5 p. - Published in : Phys. Rev. Lett. 114 (2015) 091301 Fulltext: PDF; External link: Preprint

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2014-11-11
08:12
Why should we care about the top quark Yukawa coupling? / Bezrukov, Fedor (CERN ; Connecticut U. ; RIKEN BNL) ; Shaposhnikov, Mikhail (IPT, Lausanne)
In the cosmological context, for the Standard Model to be valid up to the scale of inflation, the top quark Yukawa coupling $y_t$ should not exceed the critical value $y_t^{crit}$, coinciding with good precision (about 0.02%) with the requirement of the stability of the electroweak vacuum. So, the exact measurements of $y_t$ may give an insight on the possible existence and the energy scale of new physics above 100 GeV, which is extremely sensitive to $y_t$. [...]
arXiv:1411.1923; CERN-PH-TH-2014-218.- 2014 - 8 p. - Published in : Z. Eksp. Teor. Fiz.: 147 (2015) , pp. 3 Fulltext: PDF; External link: Preprint

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2014-11-06
08:31
Approach to equilibrium in weakly coupled nonabelian plasmas / Kurkela, Aleksi (CERN) ; Lu, Egang (McGill U.)
We follow the time evolution of nonabelian gauge bosons from far-from-equilibrium initial conditions to thermal equilibrium by numerically solving an effective kinetic equation that becomes accurate in the weak coupling limit. We consider initial conditions that are either highly overoccupied or underoccupied. [...]
arXiv:1405.6318; CERN-PH-TH-2014-093.- 2014 - 6 p. - Published in : Phys. Rev. Lett. 113 (2014) 182301 APS published version, local copy: PDF; Fulltext: PDF; External link: Preprint

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