,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,*,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,*,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,*,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,*,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,*,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,*,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,*,Particle Cosmology,季向东 上海交通大学,Particle Cosmology季向东,Outline,Particle Cosmology,WIMPs Miracle,PandaX,Outline Particle Cosmology,What is particle cosmology?,Can particle physicists say something about cosmology?,Or vice versa,can cosmologists say something about particle physics?,Particle Physics=Standard Model,+a bunch of untested ideas,(planck scale,GUT,SUSY,extra dimension,LR symmetry,techni-color,little Higgs),What is particle cosmology?Can,Importance issues,What is dark matter?Why there is 23%dark matter?,Why there is 4%baryonic matter?,Can particle physicists say something about cosmological constant?,Other questions:,What is the role of neutrinos?,Particle physics from cosmology?,The early universe is an important lab for particle physics,Importance issues What is dark,The Cooking recipe,Assuming Standard Cosmology+(nearly)thermal equilibrium,The third magic assumption!,Throw in some particles,everything that we know,quarks+leptons+.,forming the energy-momentum density,Solve the Einstein equation.,The Cooking recipeAssuming Sta,Particle and interactions,gravity weak strong e/m,Quarks,Lepton+,(W,H+),Neutrinos ,(Z,H0),Photons,Gluons ,Gravitons ,Symmetries:spacetime+gauge symmetries+other,Particle and interactions,There are unknowns,Heavy particles that live short.,In the GUT model,there are GUT scales multiplets which play important role in the very early universe,Heavy right-handed neutrinos,Particles that are weakly interacting and live long,Axions,Sterile neutrinos,Gravitino,WIMPs,.,There are unknowns Heavy parti,Particles that live long,Electron:,lightest charged particle(charge conservation),Proton:,baryon number symmetry breaking interaction is small.,Neutrinos:,lightest fermion,Photon and graviton:,cannot decay due to energy-momentum conservation,Particles that live longElectr,Particles that drop out of thermal equilibrium,Standard Boltzmann equation approach,Depend on the rate of annihilation and recombination,Can trace out particles cosmic history fairly accurately,Particles that drop out of the,Baryon Asymmetry and Leptogenesis,Understanding baryon-antibaryon asymmetry in the present universe,why matter dominates over antimatter?,Heavy right-handed neutrino required by seasaw might play a very important role,Constraint on the CP violation parameter in the lepton sector,Baryon Asymmetry and Leptogene,What is dark matter?,Axion,Sterile neutrinos,Gravitinos,WIMPs,Non-particle possibilities,What is dark matter?Axion,Gravitino dark matter?,Because of its weak gravity coupling,gravitino decouples from the rest of the world very early,left with a huge quantity(it must be very light to avoid over-closure).,It can be diluted through inflation,Gravitino will be regenerated through reheating process.,If gravitino decays,its life time will be around M,2,pl,/M,3,which could affect BBN.,Gravitino dark matter?Becaus,Gravitino dark matter?,If gravitino is the lightest supersymmetric particle,it lives long,However,decay(to gravitino)of the next-to-the lightest supersymmetric particles can affect BBN,This problem can be solve through small R-parity breaking decays,which lead to a gravitino with life time much longer than that of the universe.,Gravitino dark matter?If grav,WIMPs,WIMPs are particles that have mass on the order of electroweak symmetry breaking scale and has only weak interactions,WIMPs has long life-time due to certain symmetry,Z2 symmetry,U(1)symmetry,R-parity,WIMPsWIMPs are particles that,Dark Matter Relics in the Universe,T M,WIMPs in thermal equilibrium,T M,number density becomes Boltzmann suppressed,T M/20,Hubble expansion dominates over annihilations freeze-out occurs,Precise temperature at which freeze-out occurs,and the density which results,depends on the WIMPs annihilation cross section,Dark Matter Relics in the Univ,WIMP,Miracle,To understand the percent of DM energy in the universe today,we need the DM particles having annihilation cross sections on the order of,10,-40,cm,2,Therefore,apart from the gravitational interactions,the DM particles probably have weak interactions as well!,If DM particles do have weak interactions,they may have something to do with the