CERN Accelerating science

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2017-04-19
08:09
Flavour anomalies after the $R_{K^*}$ measurement / D'Amico, Guido (CERN) ; Nardecchia, Marco (CERN) ; Panci, Paolo (CERN) ; Sannino, Francesco (CERN ; U. Southern Denmark, CP3-Origins ; U. Southern Denmark, Odense, DIAS) ; Strumia, Alessandro (CERN ; Pisa U. ; INFN, Pisa) ; Torre, Riccardo (EPFL, Lausanne, LPTP) ; Urbano, Alfredo (CERN)
The LHCb measurement of the $\mu/e$ ratio $R_{K^*}$ indicates a deficit with respect to the Standard Model prediction, supporting earlier hints of lepton universality violation observed in the $R_K$ ratio. We show that the $R_K$ and $R_{K^*}$ ratios alone constrain the chiralities of the states contributing to these anomalies, and we find deviations from the Standard Model at the $4\sigma$ level. [...]
CERN-TH-2017-086; CP3-ORIGINS-2017-014; IFUP-TH-2017; arXiv:1704.05438.- 2017-09-04 - 31 p. - Published in : JHEP 09 (2017) 010 Article from SCOAP3: PDF; Preprint: PDF;

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2017-04-15
08:30
Multi-loop calculations: numerical methods and applications / Borowka, S. (CERN) ; Heinrich, G. (Munich, Max Planck Inst.) ; Jahn, S. (Munich, Max Planck Inst.) ; Jones, S.P. (Munich, Max Planck Inst.) ; Kerner, M. (Munich, Max Planck Inst.) ; Schlenk, J. (Durham U., IPPP)
We briefly review numerical methods for calculations beyond one loop and then describe new developments within the method of sector decomposition in more detail. [...]
CERN-TH-2017-051 ; IPPP-17-28 ; MPP-2017-62 ; arXiv:1704.03832.
- 10 p.
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2017-04-15
08:30
Anomaly-Free Dark Matter Models are not so Simple / Ellis, John (King's Coll. London ; CERN) ; Fairbairn, Malcolm (King's Coll. London) ; Tunney, Patrick (King's Coll. London)
We explore the anomaly-cancellation constraints on simplified dark matter (DM) models with an extra U(1)$^\prime$ gauge boson $Z'$. We show that, if the Standard Model (SM) fermions are supplemented by a single DM fermion $\chi$ that is a singlet of the SM gauge group, and the SM quarks have non-zero U(1)$^\prime$ charges, the SM leptons must also have non-zero U(1)$^\prime$ charges, in which case LHC searches impose strong constraints on the $Z'$ mass. [...]
KCL-PH-TH-2017-21; CERN-TH-2017-084; arXiv:1704.03850.- 2017-08-16 - 19 p. - Published in : JHEP 08 (2017) 053 Article from SCOAP3: PDF; Preprint: PDF;

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2017-04-13
08:29
Single top polarisation as a window to new physics / Aguilar-Saavedra, J.A. (Granada U., Theor. Phys. Astrophys.) ; Degrande, C. (CERN) ; Khatibi, S. (IPM, Tehran)
We discuss the effect of heavy new physics, parameterised in terms of four-fermion operators, in the polarisation of single top (anti-)quarks in the $t$-channel process at the LHC. It is found that for operators involving a right-handed top quark field the relative effect on the longitudinal polarisation is twice larger than the relative effect on the total cross section. [...]
CERN-TH-2017-013; arXiv:1701.05900.- 2017-06-10 - 9 p. - Published in : Phys. Lett. B 769 (2017) 498-502 Article from SCOAP3: PDF; Elsevier Open Access article: PDF; Fulltext: PDF;

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2017-04-12
07:18
Colorful Twisted Top Partners and Partnerium at the LHC / Kats, Yevgeny (CERN ; Ben Gurion U. of Negev ; Weizmann Inst.) ; McCullough, Matthew (CERN) ; Perez, Gilad (Weizmann Inst.) ; Soreq, Yotam (MIT, Cambridge, CTP) ; Thaler, Jesse (MIT, Cambridge, CTP)
In scenarios that stabilize the electroweak scale, the top quark is typically accompanied by partner particles. In this work, we demonstrate how extended stabilizing symmetries can yield scalar or fermionic top partners that transform as ordinary color triplets but carry exotic electric charges. [...]
MIT-CTP-4897; CERN-TH-2017-073; arXiv:1704.03393.- 2017-06-23 - 34 p. - Published in : JHEP 06 (2017) 126 Article from SCOAP3: PDF; Preprint: PDF;

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2017-04-11
08:06
Where is Particle Physics Going? / Ellis, John (King's Coll. London ; CERN)
The answer to the question in the title is: in search of new physics beyond the Standard Model, for which there are many motivations, including the likely instability of the electroweak vacuum, dark matter, the origin of matter, the masses of neutrinos, the naturalness of the hierarchy of mass scales, cosmological inflation and the search for quantum gravity [...]
KCL-PH-TH-2017-18 ; CERN-TH-2017-080 ; arXiv:1704.02821.
- 20 p.
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2017-04-08
07:18
An Investigation of New Methods for Numerical Stochastic Perturbation Theory in $\varphi^4$ Theory / Dalla Brida, Mattia (Milan Bicocca U. ; INFN, Milan Bicocca) ; Garofalo, Marco (U. Edinburgh, Higgs Ctr. Theor. Phys.) ; Kennedy, A.D. (U. Edinburgh, Higgs Ctr. Theor. Phys.)
Numerical stochastic perturbation theory is a powerful tool for estimating high-order perturbative expansions in lattice field theory. The standard algorithms based on the Langevin equation, however, suffer from several limitations which in practice restrict the potential of this technique. [...]
CERN-TH-2017-059; arXiv:1703.04406.- 2017-09-06 - 22 p. - Published in : Phys. Rev. D 96 (2017) 054502 Preprint: PDF;

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2017-04-05
07:33
Radiative symmetry breaking from interacting UV fixed points / Abel, Steven (Durham U., IPPP ; CERN) ; Sannino, Francesco (CERN ; U. Southern Denmark, CP3-Origins ; U. Southern Denmark, Odense, DIAS)
It is shown that the addition of positive mass-squared terms to asymptotically safe gauge-Yukawa theories with perturbative UV fixed points leads to calculable radiative symmetry breaking in the IR. This phenomenon, and the multiplicative running of the operators that lies behind it, is akin to the radiative symmetry breaking that occurs in the Supersymmetric Standard Model..
CERN-TH-2017-066; CP3-ORIGINS-2017-011-DNRF90; IPPP-2017-23; arXiv:1704.00700.- 2017-09-28 - 14 p. - Published in : Phys. Rev. D 96 (2017) 056028 Preprint: PDF;

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2017-03-31
07:54
Wilson lines and UV sensitivity in magnetic compactifications / Ghilencea, D.M. (Bucharest, IFIN-HH) ; Lee, Hyun Min (Chung-Ang U.)
We investigate the ultraviolet (UV) behaviour of 6D N=1 supersymmetric effective (Abelian) gauge theories compactified on a two-torus ($T_2$) with magnetic flux. To this purpose we compute offshell the one-loop correction to the Wilson line state self-energy. [...]
CERN-TH-2017-072; arXiv:1703.10418.- 2017-06-07 - 13 p. - Published in : JHEP 06 (2017) 039 Article from SCOAP3: PDF; Preprint: PDF;

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2017-03-31
07:54
Continuum limit and universality of the Columbia plot / de Forcrand, Philippe (ETH, Zurich (main) ; CERN) ; D'Elia, Massimo (INFN, Pisa ; Pisa U.)
Results on the thermal transition of QCD with 3 degenerate flavors, in the lower-left corner of the Columbia plot, are puzzling. [...]
arXiv:1702.00330 ; CERN-TH-2017-022.
- 7 p.
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