Baryogenesis and Dark Matter from $ B $ Mesons

KCL-18-53, IFIC-18-35 Baryogenesis and Dark Matter from B Mesons 1, 2, 3, 1, Gilly Elor, ∗ Miguel Escudero, y and Ann E. Nelson z 1Department of Physics, Box 1560, University of Washington, Seattle, WA 98195, U.S.A. 2From 09/18: Department of Physics, King's College London, Strand, London WC2R 2LS, UK 3Instituto de F´ısica Corpuscular (IFIC), CSIC-Universitat de València,Paterna E-46071, Valencia, Spain We present a new mechanism of Baryogenesis and dark matter production in which both the dark matter relic abundance and the baryon asymmetry arise from neutral B meson oscillations and subsequent decays. This set-up is testable at hadron colliders and B-factories. In the early Universe, decays of a long lived particle produce B mesons and anti-mesons out of thermal equilibrium. These mesons/anti-mesons then undergo CP violating oscillations before quickly decaying into visible and dark sector particles. Dark matter will be charged under Baryon number so that the visible sector baryon asymmetry is produced without violating the total baryon number of the Universe. The produced baryon asymmetry will be directly related to the leptonic charge asymmetry in neutral B decays; an experimental observable. Dark matter is stabilized by an unbroken discrete symmetry, and proton decay is simply evaded by kinematics. We will illustrate this mechanism with a model that is unconstrained by di-nucleon decay, does not require a high reheat temperature, and would have unique experimental signals { a positive leptonic asymmetry in B meson decays, a new decay of B mesons into a baryon and missing energy, and a new decay of b-flavored baryons into mesons and missing energy. These three observables are testable at current and upcoming collider experiments, allowing for a distinct probe of this mechanism. I. INTRODUCTION DM carries a conserved charge just as baryons do. Most models of Baryogenesis and/or DM production involve The Standard Model of Particle Physics (SM), while very massive particles and high temperatures in the early now tested to great precision, leaves many questions Universe, making them impossible to test directly and unanswered. At the forefront of the remaining mysteries in conflict with cosmologies requiring a low inflation or is the quest for dark matter (DM); the gravitationally reheating scale. inferred but thus far undetected component of matter In this work we present a new mechanism for Baryo- which makes up roughly 26% of the energy budget of the genesis and DM production that is unconstrained by nu- Universe [1,2]. Many models have been proposed to ex- cleon or dinucleon decay, accommodates a low reheating scale T (10 MeV), and has distinctive experimen- plain the nature of DM, and various possible production RH ∼ O mechanisms to generate the the DM relic abundance { tal signals. 2 measured to be ΩDMh = 0:1200 0:0012 [2] { have been We will consider a scenario where b-quarks and anti- proposed. However, experiments± searching for DM have quarks are produced by late, out of thermal equilibrium, yet to shed light on its nature. decays of some heavy scalar field Φ (which can be, for Another outstanding question may be stated as fol- instance, the inflaton or a string modulus). The pro- lows: why is the Universe filled with complex mat- duced quarks hadronize to form neutral B-mesons and ter structures when the standard model of cosmology anti-mesons which quickly undergo CP violating oscilla- 1 predicts a Universe born with equal parts matter and tions , and decay into a dark sector via a ∆B = 0 four anti-matter? A dynamical mechanism, Baryogenesis, is Fermi operator i.e. a component of DM is assumed to be required to generate the primordial matter-antimatter charged under baryon number. In this way the baryon 11 number violation Sakharov condition is \relaxed" to an asymmetry; YB (nB nB¯ )=s = (8:718 0:004) 10− , inferred from measurements≡ − of the Cosmic± Microwave× apparent violation of baryon number in the visible sector arXiv:1810.00880v3 [hep-ph] 21 Feb 2019 Background (CMB) [1,2] and Big Bang Nucleosynthe- due to a sharing with the dark sector (in similar spirit to sis (BBN) [3,4]. A mechanism of Baryogenesis must [13, 14]). The decay of B mesons into baryons, mesons satisfy the three Sakharov conditions [5]; C and CP Vi- and missing energy would be a distinct signature of our olation (CPV), baryon number violation, and departure mechanism that can be searched for at experiments such from thermal equilibrium. as Belle-II. Additionally, the ∆B = 0 operator allows us It is interesting to consider models and mechanisms to circumvent constraints arising in models with baryon that simultaneously generate a baryon asymmetry and number violation. produce the DM abundance in the early Universe. For instance, in models of Asymmetric Dark Matter [6{11], 1 For instance, the SM box diagrams that mediate the meson anti- meson oscillations contain CP violating phases due to the CKM ∗ [email protected] matrix elements in the quark-W vertices (see for instance [4] for y [email protected] a review). Additionally, models of new physics may introduce [email protected] additional sources of CPV to the B0 B¯0 system [12]. z − 16 And now we can clearly compare the decay and annihi- 4. B meson decay operators lation rates: ∆n Γ Γ2 B B = B (45) ∆n2 σv Γ σv n (t) B h i Φ h i Φ where in the last step we have assumed that the Φ field does not completely dominate the Universe so that we can use t 1/(2H). When solving numerically for Φ number density⇠ we found that even with an annihilation cross section of σv = 10 mb, the decay rate over- h i comes the annihilation rate for T & 100 MeV even for Here we categorize the lightest final states for all the 21 Γφ = 10− GeV. Thus, for practical purposes it is safe quark combinations that allow for B mesons to decay into to ignore the e↵ect of annihilations in the Boltzmann a visible baryon plus dark matter. Note that the mass equation (16). di↵erence between final an initial state will give an upper bound on the dark Dirac baryon .InMeVunits,the masses of the di↵erent hadrons read: mBd = 5279.63, m = 5366.89, m + = 5279.32, m 0 = 2471.87, 3. Dark Cross Sections Bs B ⌅c m + = 2468.96, m = 938.27, m = 939.56, m = ⌅c p n ⇤ + 0 Here we list the dark sector cross sections to lowest 1115.68, m⌃ = 1189.37, m⌅ = 1314.86, m⌦c = 2695.2, m = 2286.46 and m = 139.57. The corresponding order in velocity v that result from the interaction (5): ⇤c ⇡− final state and mass di↵erences are summarized in Ta- ble III. 4 2 3/2 yd (m⇠ + m ) [(mφ m⇠)(m⇠ + mφ)] σφ?φ ⇠⇠ = − , ! 2 2⇡m3 m2 + m2 + m2 φ − ⇠ φ ⇣2 4 ⌘ v yd 2 ? σ⇠⇠ φ φ mφ 0 = 4 (46) ! | ! 2 2 ⇥ Out 48of equilibrium⇡ m⇠ + m B-mesons decay into CP violating oscillations late time decay Dark Matter and hadrons Baryogenesis 5 4 2 ⇣ 3 3 ⌘ + 0 0 ⇠ 11 2m⇠m +5m⇠m +8¯ m⇠m B B Bs Dark Matter YB =8.7 10− b d ⇥ 2 4 Φ 5 6 6 φ anti-Baryon +9m m +6m m +3m +3m B & ⇥ ⇠ ⇠ ⇠ ) b ¯0 ¯0 Baryon B− Bd Bs ⇤ ⇤ Dark Matter d s 2 TRH 20 MeV A A BR(B ⇠ + Baryon + ...) ⌦ h =0.12 ⇠ `` `` ! DM FIG. 1. Summary of our mechanism for generating the baryon asymmetry and DM relic abundance. b-quarks and anti-quarks [1] P. A. R. Adeare produced et al. during (Planck), a late era in the Astron. history of the early Astrophys. Universe, namely594TRH , (10 MeV), and88 hadronize,045002(2016),1511.09466. into charged and neutral B-mesons. The neutral B0 and B¯0 mesons quickly undergo CPV oscillations∼ O before decaying out of thermal equilibrium A13 (2016),into 1502.01589. visible baryons, dark sector scalar baryons φ and dark Majorana fermions ξ. Total Baryon[15] numberA. Lenz is conserved and and U. the Nierste, in CKM unitarity triangle. Pro- dark sector therefore carries anti-baryon number. The mechanism requires of a positive leptonic asymmetry in B-meson decays [2] N. Aghanimq et al. (Planck) (2018), 1807.06209. ceedings, 6th International Workshop, CKM 2010, War- (A``), and the existence of a new decay of B-mesons into a baryon and missing energy. Both these observables are testable at [3] R. H. Cyburt,current B. and upcomingD. Fields, collider experiments. K. A. Olive, and T.-H. Yeh, wick, UK, September 6-10, 2010 (2011), 1102.4274. Rev. Mod. Phys. 88,015004(2016),1505.01076. [16] F. J. Botella, G. C. Branco, M. Nebot, and A. Snchez, We will show that the CPV required for Baryogenesis is We summarize the key components of our set-up which [4] M. Tanabashidirectly et related al. to an (ParticleDataGroup), experimental observable in neutral Phys.will be Rev.further elaborated uponPhys. in the following Rev. sections:D91,035013(2015),1402.1181. B meson decays { the leptonic charge asymmetry Aq . D98,030001(2018). `` [17] W. Altmannshofer, S. Gori, M. Pospelov, and I. Yavin, Schematically, A heavy scalar particle Φ late decays out of thermal [5] A. D. Sakharov, Pisma Zh. Eksp. Teor. Fiz. 5,32(1967),• equilibrium to b quarks andPhys. anti-quarks. Rev. D89,095033(2014),1403.1269. Y Aq Br(B0 φ ξ + Baryon + X) ; (1) B / `` × q ! Since temperatures are low, a large fraction of these [Usp. Fiz.

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