Affleck-Dine baryogenesis in type IIB string models

Published for SISSA by Springer Received: April 20, 2016 Revised: June 6, 2016 Accepted: June 14, 2016 Published: June 27, 2016 Rouzbeh Allahverdi,a Michele Cicolib,c,d and Francesco Muiab,c a Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM 87131, U.S.A. b Dipartimento di Fisica e Astronomia, Università di Bologna, via Irnerio 46, 40126 Bologna, Italy c INFN, Sezione di Bologna, via Irnerio 46, 40126 Bologna, Italy d ICTP, Strada Costiera 11, Trieste 34014, Italy E-mail: , , Abstract: We propose a possible string embedding of Affleck-Dine baryogenesis in type IIB sequestered models where the late-time decay of the lightest modulus reheats the universe to relatively low temperatures. We show that if inflation is driven by a blow-up Kähler modulus, the Affleck-Dine field can become tachyonic during inflation if the Kähler metric for matter fields has an appropriate inflaton-dependent contribution. We find that the Affleck-Dine mechanism can generate the observed baryon asymmetry for natural values of the underlying parameters which lead also to successful inflation and low-energy gaugino masses in a split supersymmetry scenario. The reheating temperature from the lightest modulus decay is high enough to allow thermal Higgsino-like dark matter. Keywords: Strings and branes phenomenology, Supersymmetry Phenomenology ArXiv ePrint: 1604.03120 Open Access, c The Authors. Article funded by SCOAP3 . doi:10.1007/JHEP06(2016)153 JHEP06(2016)153 Affleck-Dine baryogenesis in type IIB string models Contents 1 2 Review of Affleck-Dine baryogenesis 2.1 Basic mechanism 2.2 Supergravity constraints 3 3 5 3 Sequestered Large Volume Scenario 3.1 Setup of the compactification 3.2 Soft-terms 5 5 11 4 Inflation, reheating and Affleck-Dine baryogenesis 4.1 Inflationary dynamics 4.2 Dynamics of the Affleck-Dine field 4.3 Reheating from lightest modulus decay 4.4 Generation of baryon asymmetry 14 14 16 18 20 5 Results and discussion 5.1 Numerical results 5.2 Origin of dark matter abundance 21 21 21 6 Conclusions 24 1 Introduction The origin of the matter-antimatter asymmetry of the universe still remains a mystery to be unraveled [1, 2]. Most current approaches are based on mechanisms that rely on relatively high reheating temperatures Trh . For example, thermal leptogenesis [3, 4] requires Trh & 109 –1010 GeV while electroweak baryogenesis [5] demands Trh & 1 TeV. However, supersymmetric (SUSY) extensions of the Standard Model (SM) and their string theory embeddings typically have moduli fields that alter the standard thermal history of the universe [6]. The moduli, due to their gravitational coupling to matter, are long-lived and tend to dominate the energy density of the universe before decaying. The late-time decay of the moduli typically gives rise to reheating temperatures well below the electroweak scale, particularly in models with low-energy SUSY. The moduli decay also releases a huge amount of entropy that dilutes any pre-existing relic abundance, thereby necessitating the production of dark matter (DM) and the generation of the baryon asymmetry of the universe (BAU) at relatively low temperatures. –1– JHEP06(2016)153 1 Introduction • Small-field inflation takes place in the closed string sector where a blow-up modulus σ drives the exponential expansion of the universe in agreement with Planck data [25]. Generating density perturbations with the correct amplitude raises all the mass scales mentioned above by about two orders of magnitude, which results in gaugino masses in the range M ∼ 104 –105 GeV. • If the Kähler metric for matter fields has an appropriate dependence on σ, in split SUSY-like models squarks and sleptons can become tachyonic during inflation. The AD field φ can then develop a sufficiently large non-zero VEV during inflation. Moreover also the volume mode χ is shifted from its late-time minimum during inflation. • At the end of inflation, the inflaton becomes very heavy since mσ ∼ m3/2 and its decay leads to an initial stage of reheating with a relatively high temperature. When –2– JHEP06(2016)153 An interesting class of string compactifications is type IIB sequestered string models with D3-branes at singularities [7–9]. These models have been explicitly embedded in globally consistent Calabi-Yau (CY) compactifications with de Sitter (dS) closed string moduli stabilisation [10, 11]. Moreover, they can yield low-energy SUSY without introducing any cosmological moduli problem [12–14] or gravitino overproduction problem [15, 16], and provide a promising framework for building inflationary models in agreement with Planck data where the inflaton is a Kähler modulus [17–19]. In the context of the Large Volume Scenario (LVS) [20, 21], all sequestered models share a universal feature: the overall volume mode is the lightest modulus χ. Its mass is √ suppressed with respect to the gravitino mass: mχ ∼ m3/2 ǫ, where ǫ ∼ m3/2 /Mp ≪ 1. On the other hand gaugino masses scale as M ∼ m3/2 ǫ while scalar masses can behave as either m0 ∼ M or m0 ∼ mχ [22, 23] depending on the exact form of the Kähler metric for matter fields and the mechanism responsible for achieving a dS vacuum. Thus sequestered scenarios can give rise to both MSSM-like and split SUSY-like models. TeV-scale gaugino masses can be obtained for m3/2 ∼ 1010 –1011 GeV and mχ ∼ 106 –107 GeV. The decay of χ p typically gives rise to a reheating temperature of order Trh ∼ mχ mχ /Mp ∼ O(10) GeV. A promising mechanism for generating the observed value of BAU in models with reheating temperatures below the EW scale is Affleck-Dine (AD) baryogenesis [24]. This scenario utilizes a SUSY D-flat direction that carries a non-zero baryon number, the socalled AD field. If the AD field develops a sufficiently large displacement from its late-time minimum during inflation, its post-inflationary dynamics can generate a baryon asymmetry that can survive the entropy release during the final stage of reheating. However, a successful embedding of AD baryogenesis in supergravity models is non-trivial as supergravity corrections can ruin the flatness of the potential for the AD field, thereby preventing it from acquiring a large vacuum expectation value (VEV) during inflation. In this paper, we show that BAU can be successfully generated in sequestered models via AD mechanism. In particular, we shall outline how to construct a model where one can follow the whole cosmological evolution of the universe from inflation to the final stage of reheating by decay of the lightest modulus which successfully generates the observed BAU along with the correct DM relic abundance. The highlights of the scenario are as follows: the Hubble constant H drops to mφ ∼ mχ , both φ and χ start oscillating around their late-time minima. The SUSY breaking A-terms induce a rotational motion of the AD field and the generation of baryon asymmetry that gets transferred to quarks when φ decays. We wo (...truncated)