arXiv subjects

Isabel Garcia Garcia

Publications and source records attributed to Isabel Garcia Garcia.

21 records · Page 2Linked to original sources

arXiv2017

LHCb anomalies from a natural perspective

Tension between the Standard Model (SM) and data concerning $b \rightarrow s$ processes has become apparent. Most notoriously, concerning the $R_K$ ratio, which probes lepton non-universality in $b$ decays, and measurements involving the decays $B \rightarrow K^* μ^+ μ^-$ and $B_s \rightarrow ϕμ^+ μ^-$. Careful analysis of a wide range of $b \rightarrow s$ data shows that certain kinds of new physics can significantly ameliorate agreement with experiment. Here, we show that these $b \rightarrow s$ anomalies can be naturally accommodated in the context of Natural Scherk-Schwarz Theories of the Weak Scale -- a class of models designed to address the hierarchy problem. No extra states need to be introduced in order to accommodate these anomalies, and the assumptions required regarding flavor violating couplings are very mild. Moreover, the structure of the theory makes sharp predictions regarding $B$ meson decays into final states including $τ^+ τ^-$ pairs, which will provide a future test of these models.

hep-ph↗

arXiv2016

The String Soundscape at Gravitational Wave Detectors

We argue that gravitational wave (GW) signals due to collisions of ultra-relativistic bubble walls may be common in string theory. This occurs due to a process of post-inflationary vacuum decay via quantum tunnelling within (Randall-Sundrum-like) warped throats. Though a specific example is studied in the context of type IIB string theory, we argue that our conclusions are likely more general. Many such transitions could have occurred in the post-inflationary Universe, as a large number of throats with exponentially different IR scales can be present in the string landscape, potentially leading to several signals of widely different frequencies -- a soundscape connected to the landscape of vacua. Detectors such as eLISA and AEGIS, and observations with BBO, SKA and EPTA (pulsar timing) have the sensitivity to detect such signals, while at higher frequency aLIGO is not yet at the required sensitivity. A distribution of primordial black holes is also a likely consequence, though reliable estimates of masses and $Ω_{\rm pBH} h^2$ require dedicated numerical simulations, as do the fine details of the GW spectrum due to the unusual nature of both the bubble walls and transition.

hep-ph↗

arXiv2015

Natural Scherk-Schwarz Theories of the Weak Scale

Natural supersymmetric theories of the weak scale are under growing pressure given present LHC constraints, raising the question of whether untuned supersymmetric (SUSY) solutions to the hierarchy problem are possible. In this paper, we explore a class of 5-dimensional natural SUSY theories in which SUSY is broken by the Scherk-Schwarz mechanism. We pedagogically explain how Scherk-Schwarz elegantly solves the traditional problems of 4-dimensional SUSY theories (based on the MSSM and its many variants) that usually result in an unsettling level of fine-tuning. The minimal Scherk-Schwarz set up possesses novel phenomenology, which we briefly outline. We show that achieving the observed physical Higgs mass motivates extra structure that does not significantly affect the level of tuning (always better than $\sim 10\%$) and we explore three qualitatively different extensions: the addition of extra matter that couples to the Higgs, an extra $U(1)^\prime$ gauge group under which the Higgs is charged and an NMSSM-like solution to the Higgs mass problem.

hep-ph↗