DOCSLIB.ORG

Big Bang Nucleosynthesis

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Big Bang Nucleosynthesis Big Bang Nucleosynthesis Subir Sarkar xford hysics TM v Introduction v Physical context v Nuclear reactions v Primordial abundances v Cross-check with CMB v Constraints on fundamental physics Master class, The Ninth Quantum Universe Symposium, Groningen, 17 April 2019 The universe is made mainly of hydrogen (~75%) and helium (~25%) + traces of heavier elements Where did all the elements come from? :547,1957 29 ---------------------------------- -------------------------------- Neutron-star mergers (‘kilonova’) Burbidge, Burbidge, Fowler & Hoyle, RMP George Gamow is generally credited with having founded the theory of primordial nucleosynthesis and, as a corollary, predicted the temperature of the relic radiation The real story is that while Gamow had brilliant ideas, he could not calculate too well, so enlisted the help of graduate student Ralph Alpher and posdoc Robert Herman … Ref. 1) was published on 1 April 1948 - including Bethe (who had nothing to do with it) … but leaving out Herman because he “stubbornly refused to change his name to Delter”! The modern theory of primordial nucleosynthesis is based essentially on this paper … which followed the crucial observation by Hayashi (Prog.Theoret.Phys.5:224,1950) that neutrons and protons are in chemical equilibrium in the hot early universe Ralph Alpher was belatedly awarded the US National Medal of Science (2005): “For his unprecedented work in the areas of nucleosynthesis, for the prediction that universe expansion leaves behind background radiation, and for providing the model for the Big Bang theory” The Standard Model of the Early Universe Radiation-dominated plasma in thermal equilibrium (very close to Einstein-deSitter: Wm=1, Wk=0, WL=0) Number density: Energy density: Entropy density: where, the number of relativistic degrees of freedom sum over all bosons and fermions with appropriate weight: number energy Knowing the equation of state, we can solve the Friedman equation … For matter: ⇒ ⇒ ➪ Hence ⇒ For radiation: ⇒ So radiation will dominate over all other components as we go to early times ⇒ Radiation-dominated era But at the matter density will come to dominate Note that during matter-domination too Evolution of different energy components matter-radiation equality -4 ρr ~ a log (r) -3 ρm ~ a present epoch ρΛ -4 0 log(a) Very recently (at z~1) the expansion has supposedly become dominated 2 2 2 by a ‘cosmological constant’: Λ ~ 2 H0 ⇒ ρΛ ~ 2 H0 MP This creates a severe ‘why now?’ problem as ρΛ << ρm,r at earlier epochs In the absence of dissipative processes (e.g. phase transitions which generate entropy) the comoving entropy is conserved: ⇒ i.e. The dynamics is governed by the Friedmann equation: Integrating this gives the time-temperature relationship: t (s) = 2.42 g-1/2 (T/MeV)-2 So we can work out when events of physical significance occurred in our past (according to the Standard Model of particle physics) The Standard Model of the Early Universe History of g (T) The phAse diAgrAm of the StAndArd Model (bAsed on A dimensionAlly reduced SU (2)L theory with quArks And leptons, with the AbeliAn hyperchArge symmetry U (1)Y neglected). The 1st-order trAnsition line ends At the 2nd-order endpoint: 2 mH ≃ 72 ± 2 GeV/c , kBTE ≃ 110 GeV; for higher Higgs mAss it is A ‘crossover’ Rummukainen et al, Nucl.Phys.B532:283,1998 To construct our thermal history we must then count all boson and fermion species contributing to the number of relativistic degrees of freedom … and take into account our understanding of (possible) phase transitions Quark-hadron ‘cross-over’ Borsanyi et al, Nature 539:69,2016 Favoured value of quark-hadron (de) confinement transition The Cosmic Microwave Background Spectrum This perfect blackbody is testimony to our hot, dense past and directly demonstrates that the expansion was indeed adiabatic (with negligible energy release) back at least to t ~ 1 day … we can go back further to t ~ 1 s by studying element synthesis The blackbody temperature can be used as a clock (assuming adiabatic expansion: aT = constant), so our thermal history can be reconstructed Nucleosynthesis (Re)combination The furthest we ‘see’ directly is back to t ~ 1 s when light elements were synthesised (the small fluctuations in CMB temperature must have been generated much earlier) Weak interactions and nuclear reactions in expanding, cooling universe (Hayashi 1950, Alpher, Follin & Herman 1953, Peebles 1966, Wagoner, Fowler & Hoyle 1967) Dramatis personae: Radiation (dominates) Matter baryon-to-photon ratio (only free parameter) Initial conditions: T >> 1 MeV, t << 1 s − n+νe ↔ p +e n-p weak equilibrium: + neutron-to-proton ratio: p +νe ↔ n + e 1/3 t T "G /G2 # τweak(n ↔ p) ≥ ⇒ $ N F % Weak freeze-out: Tf ~ 1 MeV, tf ~ 1 s universe freeze-out & ' which fixes: n p = e−(mn −mp )/Tf ≈1 6 Deuterium bottleneck: T ~ 1 → 0.07 MeV D created by but destroyed by high-E photon tail: so nucleosynthesis halted until: Tnuc ~ ΔD/-ln(η) Element synthesis: Tnuc ~ 0.07 MeV, tnuc ~ 3 min (meanwhile n/p ➛ 1/7 through neutron β-decay) 4 3 7 6 7 -5 nearly all n ➛ He (YP ~ 25% by mass) + left-over traces of D, He, Li (with Li/ Li ~ 10 ) No heavier nuclei formed in standard, homogeneous hot Big Bang … must wait for stars to form after a ~billion years and synthesise all the other nuclei in the universe (s-process, r-process, …) v Computer code by Wagoner (1969, 1973) .. updated by Kawano (1992), other codes: PArthENoPE (2007), AlterBBN (2012) v Coulomb & radiative corrections, ν heating et cetera (Dicus et al 1982) v Nucleon recoil corrections (Seckel 1993) v Covariance matrix of correlated uncertainties (Fiorentini et al 1998) v Updated nuclear cross-sections (NACRE 2003) The ‘first three minutes’ • Time < 15 s, Temperature > 3 x 109 K –universe is soup of protons, electrons and other particles … so hot that nuclei are blasted apart by high energy photons as soon as they form • Time = 15 s, Temperature = 3 x 109 K –Still too hot for Deuterium to survive –Cool enough for Helium to survive, but too few building blocks • Time = 3 min, Temperature = 109 K –Deuterium survives and is quickly fused into He –no stable nuclei with 5 or 8 nucleons, and this restricts formation of elements heavier than Helium –trace amounts of Lithium are formed • Time = 35 min, Temperature = 3 x 107 K –nucleosynthesis essentially complete (still hot enough to fuse He, but density too low for appreciable fusion) Model makes predictions about the relative abundances of the light elements 2H, 3He, 4He and 7Li, as a function of the nucleon density Primodial versus Stellar Nucleosynthesis • Timescale – Stellar Nucleosynthesis (SN): billions of years – Primordial Nucleosynthesis (PN): minutes • Temperature evolution 9Be – SN: slow increase over time – PN: rapid cooling 7Li 6Li • Density 3 – SN: 100 g/cm 4He -5 3 – PN: 10 g/cm (like air!) 3He 2H no stable nuclei • Photon to baryon ratio 1H – SN: less than 1 photon per baryon – PN: billions of photons per baryon The lack of stable elements with masses 5 and 8 make it hard for BBN (2-body processes, short time-scale) to synthesise elements beyond helium … this can be happen only in stars, on a (much) longer timescale The neutron lifetime normalises the “weak” interaction rate: τn = 880.0 ± 0.9 s (has recently dropped in value by 5σ because of one new measurement!) Uncertainties in synthesized abundances are correlated … estimate using Monte Carlo (Smith, Kawano, Malaney 1993; Krauss, Kernan 1994; Cyburt, Fields, Olive 2004) NEUTRON LIFETIME MEASUREMENT The neutron lifetime cannot be USING MAGNETICALLY TRAPPED accurately computed theoretically ULTRACOLD NEUTRONS (even knowing the weak interaction coupling GF very well) because there are corrections due to the strong interactions (which alter gA/gV away from unity) .. so it has to be measured experimentally Linear propagation of errors → → errors of propagation Linear covariance matrix (in (in agreement with Monte Carlo results) Carlo with Monte Fiorentini, Lisi, Sarkar, Villante, Phys.Rev.D58:063506,1998 BBN Predictions line widths ⇒ theoretical uncertainties (neutron lifetime, nuclear #-sections) Nucleosynthesis without a computer ⇒ … but general solution is: source sink :504,1991 378 ApJ , If … then abundances approach equilibrium values StarkmAn Freeze-out occurs when: ⇒ , HAll, Examine reAction network to identify the largest ‘source’ and ‘sink’ terms Esmailzadeh obtAin D, 3He And 7Li to , …………. within A fActor of ~2 of analytic exact numerical solution, solution and 4He to within A few % Dimopoulos … can use this formalism to determine joint dependence of abundances on expansion rate as well as baryon-to-photon ratio and so: ⇒ … can therefore employ simple χ2 statistics to determine best-fit values and uncertainties (faster than Monte Carlo + Maximum Likelihood) Lisi, Sarkar, Villante, Phys.Rev.D59:123520,1999 Inferring primordial abundances Observations of the light elements He and Li • Helium Abundance –measured in extragalactic HII regions with lowest observed abundances of heavier elements such as Oxygen and Nitrogen (i.e. smallest level of contamination from stellar nucleosynthesis) • Lithium Abundance –measured in halo Pop II stars –Lithium is easily destroyed hence observe the transition from low mass stars (low surface temp) whose core material is well mixed by convection, to higher mass stars (higher surface temp) where mixing of core is not efficient For a quantity of such fundamental cosmological importance, relatively little effort has been spent on measuring the primordial helium abundance Recent reevaluations
Load more

Recommended publications
  • Topic 3 Evidence for the Big Bang
    Topic 3 Primordial nucleosynthesis Evidence for the Big Bang ! Back in the 1920s it was generally thought that the Universe was infinite ! However a number of experimental observations started to question this, namely: • Red shift and Hubble’s Law • Olber’s Paradox • Radio sources • Existence of CMBR Red shift and Hubble’s Law ! We have already discussed red shift in the context of spectral lines (Topic 2) ! Crucially Hubble discovered that the recessional velocity (and hence red shift) of galaxies increases linearly with their distance from us according to the famous Hubble Law V = H0d where H0 = 69.3 ±0.8 (km/s)/Mpc and 1/H0 = Age of Universe Olbers’ paradox ! Steady state Universe is: infinite, isotropic or uniform (sky looks the same in all directions), homogeneous (our location in the Universe isn’t special) and is not expanding ! Therefore an observer choosing to look in any direction should eventually see a star ! This would lead to a night sky that is uniformly bright (as a star’s surface) ! This is not the case and so the assumption that the Universe is infinite must be flawed Radio sources ! Based on observations of radio sources of different strengths (so-called 2C and 3C surveys) ! The number of radio sources versus source strength concludes that the Universe has evolved from a denser place in the past ! This again appears to rule out the so-called Steady State Universe and gives support for the Big Bang Theory Cosmic Microwave Background ! CMBR was predicted as early as 1949 by Alpher and Herman (Gamow group) as a “remnant
    [Show full text]
  • Quantifying the Sensitivity of Big Bang Nucleosynthesis to Isospin Breaking
    W&M ScholarWorks Undergraduate Honors Theses Theses, Dissertations, & Master Projects 5-2016 Quantifying the Sensitivity of Big Bang Nucleosynthesis to Isospin Breaking Matthew Ramin Hamedani Heffernan College of William and Mary Follow this and additional works at: https://scholarworks.wm.edu/honorstheses Part of the Nuclear Commons Recommended Citation Heffernan, Matthew Ramin Hamedani, "Quantifying the Sensitivity of Big Bang Nucleosynthesis to Isospin Breaking" (2016). Undergraduate Honors Theses. Paper 974. https://scholarworks.wm.edu/honorstheses/974 This Honors Thesis is brought to you for free and open access by the Theses, Dissertations, & Master Projects at W&M ScholarWorks. It has been accepted for inclusion in Undergraduate Honors Theses by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. Quantifying the Sensitivity of Big Bang Nucleosynthesis to Isospin Breaking Matthew Heffernan Advisor: Andr´eWalker-Loud Abstract We perform a quantitative study of the sensitivity of Big Bang Nucleosynthesis (BBN) to the two sources of isospin breaking in the Standard Model (SM), the split- 1 ting between the down and up quark masses, δq (md mu) and the electromagnetic ≡ 2 − coupling constant, αf:s:. To very good approximation, the neutron-proton mass split- ting, ∆m mn mp, depends linearly upon these two quantities. In turn, BBN is very ≡ − sensitive to ∆m. A simultaneous study of both of these sources of isospin violation had not yet been performed. Quantifying the simultaneous sensitivity of BBN to δq and αf:s: is interesting as ∆m increases with increasing δq but decreases with increasing αf:s:. A combined analysis may reveal weaker constraints upon possible variations of these fundamental constants of the SM.
    [Show full text]
  • Cosmic Background Explorer (COBE) and Beyond
    From the Big Bang to the Nobel Prize: Cosmic Background Explorer (COBE) and Beyond Goddard Space Flight Center Lecture John Mather Nov. 21, 2006 Astronomical Search For Origins First Galaxies Big Bang Life Galaxies Evolve Planets Stars Looking Back in Time Measuring Distance This technique enables measurement of enormous distances Astronomer's Toolbox #2: Doppler Shift - Light Atoms emit light at discrete wavelengths that can be seen with a spectroscope This “line spectrum” identifies the atom and its velocity Galaxies attract each other, so the expansion should be slowing down -- Right?? To tell, we need to compare the velocity we measure on nearby galaxies to ones at very high redshift. In other words, we need to extend Hubble’s velocity vs distance plot to much greater distances. Nobel Prize Press Release The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for 2006 jointly to John C. Mather, NASA Goddard Space Flight Center, Greenbelt, MD, USA, and George F. Smoot, University of California, Berkeley, CA, USA "for their discovery of the blackbody form and anisotropy of the cosmic microwave background radiation". The Power of Thought Georges Lemaitre & Albert Einstein George Gamow Robert Herman & Ralph Alpher Rashid Sunyaev Jim Peebles Power of Hardware - CMB Spectrum Paul Richards Mike Werner David Woody Frank Low Herb Gush Rai Weiss Brief COBE History • 1965, CMB announced - Penzias & Wilson; Dicke, Peebles, Roll, & Wilkinson • 1974, NASA AO for Explorers: ~ 150 proposals, including: – JPL anisotropy proposal (Gulkis, Janssen…) – Berkeley anisotropy proposal (Alvarez, Smoot…) – Goddard/MIT/Princeton COBE proposal (Hauser, Mather, Muehlner, Silverberg, Thaddeus, Weiss, Wilkinson) COBE History (2) • 1976, Mission Definition Science Team selected by HQ (Nancy Boggess, Program Scientist); PI’s chosen • ~ 1979, decision to build COBE in-house at GSFC • 1982, approval to construct for flight • 1986, Challenger explosion, start COBE redesign for Delta launch • 1989, Nov.
    [Show full text]
  • Cities and Their Vital Systems: Infrastructure Past, Present, and Future
    Cities and Their Vital Systems: Infrastructure Past, Present, and Future i Series on Technology and Social Priorities NATIONAL ACADEMY OF ENGINEERING CitiesCitiesCities andandand TheirTheirTheir VitalVitalVital SystemsSystemsSystems Infrastructure Past, Present, and Future Jesse H. Ausubel and Robert Herman Editors NATIONAL ACADEMY PRESS Washington, D.C. 1988 Copyright National Academy of Sciences. All rights reserved. Cities and Their Vital Systems: Infrastructure Past, Present, and Future ii National Academy Press 2101 Constitution Avenue, NW Washington, DC 20418 NOTICE: The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sci- ences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievement of engineers. Dr. Robert M. White is president of the National Academy of Engineering. Funds for the National Academy of Engineering's Symposium Series on Technology and Social Priorities were provided by the Andrew W. Mellon Foundation, Carnegie Corporation of New York, and the Academy's Technology Agenda Program. This publication has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee. The views expressed in this volume are those of the authors and are not presented as the views of the Mellon Foundation, Carnegie Corporation, or the National Academy of Engineering. Library of Congress Cataloging-in-Publication Data Cities and their vital systems.
    [Show full text]
  • Arxiv:1707.01004V1 [Astro-Ph.CO] 4 Jul 2017
    July 5, 2017 0:15 WSPC/INSTRUCTION FILE coc2ijmpe International Journal of Modern Physics E c World Scientific Publishing Company Primordial Nucleosynthesis Alain Coc Centre de Sciences Nucl´eaires et de Sciences de la Mati`ere (CSNSM), CNRS/IN2P3, Univ. Paris-Sud, Universit´eParis–Saclay, Bˆatiment 104, F–91405 Orsay Campus, France [email protected] Elisabeth Vangioni Institut d’Astrophysique de Paris, UMR-7095 du CNRS, Universit´ePierre et Marie Curie, 98 bis bd Arago, 75014 Paris (France), Sorbonne Universit´es, Institut Lagrange de Paris, 98 bis bd Arago, 75014 Paris (France) [email protected] Received July 5, 2017 Revised Day Month Year Primordial nucleosynthesis, or big bang nucleosynthesis (BBN), is one of the three evi- dences for the big bang model, together with the expansion of the universe and the Cos- mic Microwave Background. There is a good global agreement over a range of nine orders of magnitude between abundances of 4He, D, 3He and 7Li deduced from observations, and calculated in primordial nucleosynthesis. However, there remains a yet–unexplained discrepancy of a factor ≈3, between the calculated and observed lithium primordial abundances, that has not been reduced, neither by recent nuclear physics experiments, nor by new observations. The precision in deuterium observations in cosmological clouds has recently improved dramatically, so that nuclear cross sections involved in deuterium BBN need to be known with similar precision. We will shortly discuss nuclear aspects re- lated to BBN of Li and D, BBN with non-standard neutron sources, and finally, improved sensitivity studies using Monte Carlo that can be used in other sites of nucleosynthesis.
    [Show full text]
  • Lecture 17 : the Cosmic Microwave Background
    Let’s think about the early Universe… Lecture 17 : The Cosmic ! From Hubble’s observations, we know the Universe is Microwave Background expanding ! This can be understood theoretically in terms of solutions of GR equations !Discovery of the Cosmic Microwave ! Earlier in time, all the matter must have been Background (ch 14) squeezed more tightly together ! If crushed together at high enough density, the galaxies, stars, etc could not exist as we see them now -- everything must have been different! !The Hot Big Bang This week: read Chapter 12/14 in textbook 4/15/14 1 4/15/14 3 Let’s think about the early Universe… Let’s think about the early Universe… ! From Hubble’s observations, we know the Universe is ! From Hubble’s observations, we know the Universe is expanding expanding ! This can be understood theoretically in terms of solutions of ! This can be understood theoretically in terms of solutions of GR equations GR equations ! Earlier in time, all the matter must have been squeezed more tightly together ! If crushed together at high enough density, the galaxies, stars, etc could not exist as we see them now -- everything must have been different! ! What was the Universe like long, long ago? ! What were the original contents? ! What were the early conditions like? ! What physical processes occurred under those conditions? ! How did changes over time result in the contents and structure we see today? 4/15/14 2 4/15/14 4 The Poetic Version ! In a brilliant flash about fourteen billion years ago, time and matter were born in a single instant of creation.
    [Show full text]
  • Baryogenesis and Dark Matter from B Mesons: B-Mesogenesis
    Baryogenesis and Dark Matter from B Mesons: B-Mesogenesis Miguel Escudero Abenza [email protected] arXiv:1810.00880, PRD 99, 035031 (2019) with: Gilly Elor & Ann Nelson Based on: arXiv:2101.XXXXX with: Gonzalo Alonso-Álvarez & Gilly Elor New Trends in Dark Matter 09-12-2020 The Universe Baryonic Matter 5% 26% Dark Matter 69% Dark Energy Planck 2018 1807.06209 Miguel Escudero (TUM) B-Mesogenesis New Trends in DM 09-12-20 !2 Theoretical Understanding? Motivating Question: What fraction of the Energy Density of the Universe comes from Physics Beyond the Standard Model? 99.85%! Miguel Escudero (TUM) B-Mesogenesis New Trends in DM 09-12-20 !3 SM Prediction: Neutrinos 40% 60% Photons Miguel Escudero (TUM) B-Mesogenesis New Trends in DM 09-12-20 !4 The Universe Baryonic Matter 5% 26% Dark Matter 69% Dark Energy Planck 2018 1807.06209 Miguel Escudero (TUM) B-Mesogenesis New Trends in DM 09-12-20 !5 Baryogenesis and Dark Matter from B Mesons: B-Mesogenesis arXiv:1810.00880 Elor, Escudero & Nelson 1) Baryogenesis and Dark Matter are linked 2) Baryon asymmetry directly related to B-Meson observables 3) Leads to unique collider signatures 4) Fully testable at current collider experiments Miguel Escudero (TUM) B-Mesogenesis New Trends in DM 09-12-20 !6 Outline 1) B-Mesogenesis 1) C/CP violation 2) Out of equilibrium 3) Baryon number violation? 2) A Minimal Model & Cosmology 3) Implications for Collider Experiments 4) Dark Matter Phenomenology 5) Summary and Outlook Miguel Escudero (TUM) B-Mesogenesis New Trends in DM 09-12-20 !7 Baryogenesis
    [Show full text]
  • The Matter – Antimatter Asymmetry of the Universe and Baryogenesis
    The matter – antimatter asymmetry of the universe and baryogenesis Andrew Long Lecture for KICP Cosmology Class Feb 16, 2017 Baryogenesis Reviews in General • Kolb & Wolfram’s Baryon Number Genera.on in the Early Universe (1979) • Rio5o's Theories of Baryogenesis [hep-ph/9807454]} (emphasis on GUT-BG and EW-BG) • Rio5o & Trodden's Recent Progress in Baryogenesis [hep-ph/9901362] (touches on EWBG, GUTBG, and ADBG) • Dine & Kusenko The Origin of the Ma?er-An.ma?er Asymmetry [hep-ph/ 0303065] (emphasis on Affleck-Dine BG) • Cline's Baryogenesis [hep-ph/0609145] (emphasis on EW-BG; cartoons!) Leptogenesis Reviews • Buchmuller, Di Bari, & Plumacher’s Leptogenesis for PeDestrians, [hep-ph/ 0401240] • Buchmulcer, Peccei, & Yanagida's Leptogenesis as the Origin of Ma?er, [hep-ph/ 0502169] Electroweak Baryogenesis Reviews • Cohen, Kaplan, & Nelson's Progress in Electroweak Baryogenesis, [hep-ph/ 9302210] • Trodden's Electroweak Baryogenesis, [hep-ph/9803479] • Petropoulos's Baryogenesis at the Electroweak Phase Transi.on, [hep-ph/ 0304275] • Morrissey & Ramsey-Musolf Electroweak Baryogenesis, [hep-ph/1206.2942] • Konstandin's Quantum Transport anD Electroweak Baryogenesis, [hep-ph/ 1302.6713] Constituents of the Universe formaon of large scale structure (galaxy clusters) stars, planets, dust, people late ame accelerated expansion Image stolen from the Planck website What does “ordinary matter” refer to? Let’s break it down to elementary particles & compare number densities … electron equal, universe is neutral proton x10 billion 3⇣(3) 3 3 n =3 T 168 cm− neutron x7 ⌫ ⇥ 4⇡2 ⌫ ' matter neutrinos photon positron =0 2⇣(3) 3 3 n = T 413 cm− γ ⇡2 CMB ' anti-proton =0 3⇣(3) 3 3 anti-neutron =0 n =3 T 168 cm− ⌫¯ ⇥ 4⇡2 ⌫ ' anti-neutrinos antimatter What is antimatter? First predicted by Dirac (1928).
    [Show full text]
  • Baryogenesis and Dark Matter from B Mesons
    Baryogenesis and Dark Matter from B mesons Abstract: In [1] a new mechanism to simultaneously generate the baryon asymmetry of the Universe and the Dark Matter abundance has been proposed. The Standard Model of particle physics succeeds to describe many physical processes and it has been tested to a great accuracy. However, it fails to provide a Dark Matter candidate, a so far undetected component of matter which makes up roughly 25% of the energy budget of the Universe. Furthermore, the question arises why there is a more matter (or baryons) than antimatter in the Universe taking into account that cosmology predicts a Universe with equal parts matter and anti-matter. The mechanism to generate a primordial matter-antimatter asymmetry is called baryogenesis. Any successful mechanism for baryogenesis needs to satisfy the three Sakharov conditions [2]: • violation of charge symmetry and of the combination of charge and parity symmetry • violation of baryon number • departure from thermal equilibrium In this paper [1] a new mechanism for the generation of a baryon asymmetry together with Dark Matter production has been proposed. The mechanism proposed to explain the observed baryon asymetry as well as the pro- duction of dark matter is developed around a fundamental ingredient: a new scalar particle Φ. The Φ particle is massive and would dominate the energy density of the Universe after inflation but prior to the Bing Bang nucleosynthesis. The same particle will directly decay, out of thermal equilibrium, to b=¯b quarks and if the Universe is cool enough ∼ O(10 MeV), the produced b quarks can hadronize and form B-mesons.
    [Show full text]
  • Origin and Evolution of the Universe Baryogenesis
    Physics 224 Spring 2008 Origin and Evolution of the Universe Baryogenesis Lecture 18 - Monday Mar 17 Joel Primack University of California, Santa Cruz Post-Inflation Baryogenesis: generation of excess of baryon (and lepton) number compared to anti-baryon (and anti-lepton) number. in order to create the observed baryon number today it is only necessary to create an excess of about 1 quark and lepton for every ~109 quarks+antiquarks and leptons +antileptons. Other things that might happen Post-Inflation: Breaking of Pecci-Quinn symmetry so that the observable universe is composed of many PQ domains. Formation of cosmic topological defects if their amplitude is small enough not to violate cosmological bounds. There is good evidence that there are no large regions of antimatter (Cohen, De Rujula, and Glashow, 1998). It was Andrei Sakharov (1967) who first suggested that the baryon density might not represent some sort of initial condition, but might be understandable in terms of microphysical laws. He listed three ingredients to such an understanding: 1. Baryon number violation must occur in the fundamental laws. At very early times, if baryon number violating interactions were in equilibrium, then the universe can be said to have “started” with zero baryon number. Starting with zero baryon number, baryon number violating interactions are obviously necessary if the universe is to end up with a non-zero asymmetry. As we will see, apart from the philosophical appeal of these ideas, the success of inflationary theory suggests that, shortly after the big bang, the baryon number was essentially zero. 2. CP-violation: If CP (the product of charge conjugation and parity) is conserved, every reaction which produces a particle will be accompanied by a reaction which produces its antiparticle at precisely the same rate, so no baryon number can be generated.
    [Show full text]
  • The Big Bang
    15- THE BIG ORIGINS BANGANAND NARAYANAN The Big Bang theory “Who really knows, who can declare? The scientific study of the origin and currently occupies When it started or where from? evolution of the universe is called the center stage in From when and where this creation has arisen cosmology. From the early years of the modern cosmology. 20th century, the observational aspects Perhaps it formed itself, perhaps it did not.” And yet, half a of scientific cosmology began to gather century ago, it was – Rig Veda (10:129), 9th century BCE. wide attention. This was because of only one among a a small series of startling discoveries few divergent world made by scientists like Edwin Hubble views, with competing hese words were written over 2000 years that changed the way we understood claims to the truth. ago. And yet, if they sound contemporary, it the physical universe. This article highlights Tis because they echo a trait that is distinctly a few trail-blazing human; the highly evolved ability of our species to Hubble had an advantage which few events in the journey look at the world around us and wonder how it all astronomers in the early 20th century of the Big Bang model came to be. How often have you asked these very had – access to the Mount Wilson from the fringes to same questions? Observatory in California. This the centerfold of particular observatory housed the astrophysics, a We assume that all things have a beginning. Could this be true for this vastly complex universe as well? largest telescopes of that time and journey that is yielded high quality data.
    [Show full text]
  • Kinetics of Spontaneous Baryogenesis
    Kinetics of Spontaneous Baryogenesis Elena Arbuzova Dubna University & Novosibirsk State University based on common work with A.D. Dolgov and V.A. Novikov arXiv:1607.01247 The 10th APCTP-BLTP/JINR-RCNP-RIKEN Joint Workshop on Nuclear and Hadronic Physics Aug. 17 - Aug. 21, 2016, RIKEN, Wako, Japan E. Arbuzova () Kinetics of SBG August 18 1 / 30 Outline Introduction Generalities about SBG Evolution of Baryon Asymmetry Kinetic Equation in Time-dependent Background Conclusions E. Arbuzova () Kinetics of SBG August 18 2 / 30 Standard Cosmological Model (SCM) The Standard Model of Cosmology: the Standard Model of particle physics ) matter content General Relativity ) gravitational interaction the inflationary paradigm ) to fix a few problems of the scenario SCM explains a huge amount of observational data: Hubble's law the primordial abundance of light elements the cosmic microwave background E. Arbuzova () Kinetics of SBG August 18 3 / 30 Some Puzzles Matter Inventory of the Universe: Baryonic matter (mainly protons and neutrons): 5%. Dark matter (weakly interactive particles not belonging to the MSM of particle physics): 25%. Dark energy: 70% of the Universe is really a mystery looking like a uniformly distributed substance with an unusual equation of state P ≈ −%. DE is responsible for the contemporary accelerated expansion of the Universe. The mechanism of inflation still remains at the level of paradigm. It does not fit the framework of the Standard Model of particle physics. Matter-antimatter asymmetry around us: the local Universe is clearly
    [Show full text]