Outlook: The Next Twenty Years. Hitoshi Murayama Lepton Photon 03 Fermilab, Aug 16, 2003

Transcription

1 Outlook: The Next Twenty Years Hitoshi Murayama Lepton Photon 03 Fermilab, Aug 16, 2003

2 Is it bright?

3 Or dark?

4 Our Field 0nbb hadron politics outreach pert. QCD B SUSY n factory LHC proton decay Higgs Dark Matter atmos n TeV reactor n K electroweak hidden dimensions LFV exotics LC CMB lattice QCD jets solar n charm Dark Energy top accelerator n e + e string

5 Big Questions Horizontal Why are there three fermion masses generations? What physics determines (large angle MSW) n 1 n 2 n 3 d s b u c e m t t the pattern of masses and mixings? mev mev ev kev MeV GeV TeV Why do neutrinos have mass yet so light? What is the origin of CP violation? What is the origin of matter anti-matter asymmetry in Universe?

6 Big Questions Vertical Why are there three unrelated gauge forces? Why is strong interaction strong? Charge quantization anomaly cancellation quantum numbers Is there a unified description of all forces? m W M P l Why is? (Hierarchy Problem) Q(3, 2, ), u(3, 1, +2 3 ), d(3, 1, 1 3 ), L(1, 2, 1 ), e(1, 1, 1) 2

7 Big Questions From the Heaven What is Dark Matter? What is Dark Energy? Why now? (Cosmic coincidence problem) What was Big Bang? Why is Universe so big? (flatness problem, horizon problem) How were galaxies and stars created?

8 Big Questions From the Hell What is the Higg boson? Why does it have negative mass-squared? Why is there only one scalar particle in the Standard Model? Is it elementary or composite? Is it really condensed in our Universe? gravity electric force weak force

9 Outlook We do not have right to expect that any of these big questions can be answered Nonetheless there is a good potential for us to answer some of them How exactly do we do it? Use supersymmetry as an example, but I expect similar stories with any scenario of TeV-scale physic

10 Outline Introduction Hell Heaven Vertical Horizontal Flavor Leptogenesis Conclusion

11 Hell gravity electric force weak force

12 The Main Obstacle We look for physics beyond the Standard Model that answers these big questions By definition, that is physics at shorter distances Then the Standard Model must survive down to whatever shorter distance scale Hierarchy problem is the main obstacle to do so We can t even get started! ~100GeV EW scale ~1TeV SM breaks down here physics that??? answers questions shorter distance

13 Once upon a time, there was a hierarchy problem... At the end of 19th century: a crisis about electron Like charges repel: hard to keep electric charge in a small pack Electron is point-like At least smaller than cm Need a lot of energy to keep it small! Dm e c 2 ~ a r e ~ GeV cm r e Correction Dm e c 2 > m e c 2 for r e < cm Breakdown of theory of electromagnetism Can t discuss physics below cm

14 Anti-Matter Comes to Rescue by Doubling of #Particles Electron creates a force to repel itself Vacuum bubble of matter anti-matter creation/ annihilation Electron annihilates the positron in the bubble only 10% of mass even for Planck-size e e e + g e g e + m e m e α 4π log(m er e ) g e e

15 Higgs repels itself, too Just like electron repelling itself because of its charge, Higgs boson also repels itself Requires a lot of energy to contain itself in its point-like size! Breakdown of theory of weak force Can t get started! H H ~100GeV ~1TeV??? H shorter distance EW scale SM breaks down here physics that answers questions Dm 2 H c 4 Ê ~ hc ˆ Á Ë r H 2

16 History repeats itself? Double #particles again superpartners Vacuum bubbles of superpartners cancel the energy required to contain Higgs boson in itself Standard Model made consistent with whatever physics at shorter distances H H H H ~ ~ W Dm 2 H ~ a m 2 SUSY 4p H H log(m H r H )

17 Opening the door Once the hierarchy problem solved, we can get started to discuss physics at shorter distances. It opens the door to the next level: Hope to answer big questions The solution to the hierarchy problem itself, e.g., SUSY, provides additional probe to physics at short distances ~100GeV EW scale ~1TeV SM SUSY breaks down here physics that??? answers questions shorter distance

18 Fermi s dream era Fermi formulated the first theory of the weak force (1933) The required energy scale to study the problem known since then: ~TeV We are finally getting there!

19 Three Directions History repeats itself Crisis with electron solved by anti-matter Double #particles again supersymmetry Learn from Cooper pairs Cooper pairs composite made of two electrons Higgs boson may be fermion-pair composite technicolor Physics as we know it ends at TeV Ultimate scale of physics: quantum gravity May have quantum gravity at TeV hidden dimensions (0.01 cm to cm)

20 More Directions Higgs boson as a Pseudo-Nambu- Goldstone boson (Little Higgs) Higgs boson as an extra-dimensional gauge boson (Gauge-Higgs Unification) No Higgs and W ± as Kaluza-Klein boson technicolorful supersymmetry

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23 Task Find physics responsible for Higgs BEC We can eliminate many possibilities at LHC But new interpretations necessarily emerge Race will be on: theorists coming up with new interpretations experimentalists excluding new interpretations A loooong process of elimination Crucial information is in details Elucidate what that physics is Reconstruct the Lagrangian from measurements

24 Absolute confidence is crucial for a major discovery As an example, supersymmetry New York Times level confidence The other half of the world discovered still a long way to Halliday-Resnick level confidence We have learned that all particles we observe have unique partners of different spin and statistics, called superpartners, that make our theory of elementary particles valid to small distances.

25 Hidden Dimensions Hidden dimensions Can emit graviton into e g the bulk 200 Events with apparent energy imbalance e s G / (fb) G LC D=10 D=9 D=8 D=7 How many extra 10 D=6 dimensions are there? E CM (GeV)

26 Supersymmetry Tevatron/LHC will discover supersymmetry Can do many measurements at LHC m 1/2 (GeV) CMS TH g(3000) ~ miss E T (100 fb -1 ) q(2000) ~ g(1500) ~ L dt = 1, 10, 100, 300 fb -1 A 0 = 0, tan = 35, m > 0 miss E T (300 fb -1 ) g(2000) ~ h(123) g(2500) ~ miss E T (10 fb -1 ) q(2500) ~ one one M l (GeV) ~ R O1 S5 400 one 200 q(500) ~ h(110) EX h 2 = 0.15 h 2 = 0.4 g(500) ~ h 2 = 1 q(1000) ~ q(1500) ~ miss E T (1 fb -1 ) g(1000) ~ cosmologically plausible region Fermilab reach: < 500 GeV one M c ~ 0 (GeV) m 0 (GeV)

27 Prove Superpartners have different spin Discovery at Tevatron Run II and/or LHC Test they are really superpartners Spins differ by 1/2 Same SU(3) SU(2) U(1) quantum numbers Supersymmetric couplings #Events Spin 0? e + e - ~ Æ m + ~ m - s = 350 GeV cos q

28 Heaven Dark Energy Dark Matter stars baryon neutrinos dark matter dark energy

29 Cosmic Microwave Background WMAP satellite result released Feb 10, 2003 h=0.71±0.04 Ω h 2 =0.135±0.009 M Ω h 2 =0.0224± b Ω =1.02±0.02 tot Yet another big step in precision cosmology >12s signal for nonbaryonic dark matter

30 Particle Dark Matter It is not dim small stars/planets (e.g., MACHOs) Fraction of the halo excluded allowed Mass / solar mass WIMP (Weakly Interacting Massive Particle) strongly favored Stable heavy particle produced in early Universe, left-over from near-complete annihilation W M = 0.756(n +1)x f n+1 g 1/ 2 s ann M Pl 3 3s 0 2 8pH ª a 2 /(TeV) 2 0 s ann TeV=10 12 ev the correct energy scale

31 Particle Dark Matter Stable, TeV-scale particle, electrically neutral, very weakly interacting No such candidate in the Standard Model Lightest Supersymmetric Particle (LSP): superpartner of a gauge boson in most models LSP a perfect candidate for WIMP Cross section [cm 2 ] (normalised to nucleon) Gaitskell&Mandic WIMP Mass [GeV] Detect Dark Matter to see it is there. Produce Dark Matter in accelerator experiments to see what it is.

32 Dark Matter: Synergy at TeV Dark Matter likely to be TeV-scale electrically neutral weakly interacting particle (e.g., LSP, Lightest KK) Accessible at accelerators (LHC & LC) Precision measurement at LC of its mass, couplings in order to calculate its cosmic abundance If it agrees with cosmological observations, we understand Universe back to sec after the Big Bang

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34 Dark Energy Why do we see matter and cosmological constant almost equal in amount? Why Now problem Actually a triple coincidence problem including the radiation If there is a deep reason for r L ~((TeV) 2 /M ) 4, Pl coincidence natural Indeed, r L ~(2meV) 4 vs (TeV) 2 /M ~0.5meV Pl r [GeV cm 3 ] equation of state w = p u / r u Flat Universe Constant w 10 4 r matter 99% 95% 90% 68% 10 2 r L 10 0 SNAP r radiation T [GeV] Supernova Cosmology Project Perlmutter et al. (1999) T now network of cosmic strings w = 1/3 range of "Quintessence" models cosmological constant w = SNAP Satellite Target Statistical Uncertainty W M = 1 - WD.E.

35 Vertical Q(3, 2, ), u(3, 1, +2 3 ), d(3, 1, 1 3 ), L(1, 2, 1 ), e(1, 1, 1) 2

36 Einstein s Dream Is there an underlying simplicity behind vast phenomena in Nature? Einstein dreamed to come up with a unified description But he failed to unify electromagnetism and gravity (GR)

37 History of Unification atoms electric magnetic planets apple electromagnetism Quantum mechanics gravity mechanics g-decay GR Special relativity Quantum ElectroDynamics Weak force Electroweak theory b-decay a-decay String theory? Grand Unification? Strong Force

38 We are just about to achieve another layer of unification HERA ep collider Unification of ds/dq 2 (pb/gev 2 ) EM H1 e + p NC prelim. ZEUS e + p NC prelim. SM e + p NC (CTEQ5D) electromagnetic and weak forces electroweak theory weak H1 e + p CC prelim. ZEUS e + p CC prelim. SM e + p CC (CTEQ5D) Long-term goal since 60s We are getting there! 10-6 The main missing link: 10-7 y < Higgs boson Q 2 (GeV 2 )

39 Superpartners as probe Most exciting thing about superpartners beyond existence: They carry information of small-distance physics to something we can gaugino mass (GeV) LHC+LC M 3 M 2 measure Are forces unified? 100 M 1 Need to see proton decay! Energy (GeV)

40 Rare Effects from High-Energies Effects of physics beyond the SM as effective operators L = L SM + 1 Λ L Λ 2 L 6 + Can be classified systematically (Weinberg) L 5 = (LH)(LH) 1 Λ (L H )(L H ) = m ννν L 6 = QQQL, Lσ µν W µν He, W µ ν W ν λ Bλ µ, (H D µ H)(H D µ H),

41 Unique Role of Neutrino Mass L 5 = (LH)(LH) 1 Λ (L H )(L H ) = m ννν Lowest order effect of physics at short distances Tiny effect (m n /E n ) 2 ~(ev/gev) 2 =10 18! Interferometry (i.e., Michaelson-Morley)! Need coherent source Need interference (i.e., large mixing angles) Need long baseline Nature was kind to provide all of them! neutrino interferometry (a.k.a. neutrino oscillation) a unique tool to study physics at very high scales Data suggest L~10 15 GeV!

42 Horizontal fermion masses d s b (large angle MSW) n 1 n 2 n 3 u c e m t t TeV GeV MeV kev ev mev mev

43 Historic Era in Flavor Physics Lepton Sector 1956 Cowan and Reines detect neutrinos from a nuclear reactor 1998 SuperK announcement of oscillation in atmospheric neutrinos 2002 SNO establishes flavor conversion in solar neutrinos 2002 KamLAND decides the solution to the solar neutrino problem Dm 2 in ev KamLAND Cl 95% exclusion by rate Ga SNO KamLAND 95% allowed by rate+shape SuperK tan 2 (Q)

44 Historic Era in Flavor Physics Lepton Sector 1956 Cowan and Reines detect neutrinos from a nuclear reactor 1998 SuperK announcement of oscillation in atmospheric neutrinos 2002 SNO establishes flavor conversion in solar neutrinos 2002 KamLAND decides the solution to the solar neutrino problem Quark Sector 1964 Fitch and Cronin discover CP violation (indirect CP in neutral K) 1999 CPLEAR establishes T violation in K mixing 2000 KTeV/NA48 establish direct CP violation in e /e 2002 BABAR/Belle establish indirect CP violation in B d meson, confirming Kobayashi- Maskawa theory

45 Question of Flavor What distinguishes different generations? Same gauge quantum numbers, yet different Hierarchy with small mixings: Need some ordered structure Probably a hidden flavor quantum number Need flavor symmetry Flavor symmetry must allow top Yukawa Other Yukawas forbidden Small symmetry breaking generates small Yukawas

46 Broken Flavor Symmetry Flavor symmetry broken by a VEV e ~0.02 SU(5)-like: 10(Q, u, e ) (+2, +1, 0) R R 5*(L, d ) (+1, +1, +1) R M u ~ Ê e 4 e 3 e 2 ˆ Á e 3 e 2 Á e Á Ë e 2, M d~ e 1 Ê e 3 e 3 e 3 ˆ Ê e 3 e 2 eˆ Á Á e 2 e 2 e 2 Á, M Á l~ e 2 e 2 Á e Á Ë e e e Ë e 3 e 2 e m u :m c :m t ~ m d 2 :m s 2 :m b 2 ~ m e 2 :m m 2 :m t 2 ~e 4 :e 2 :1 Not bad!

47 New Data from Neutrinos Neutrinos are already providing significant new information about flavor symmetries Given LMA, all mixings except U large e3 Ê big big smallˆ Ê Á Á ( e m t ) big big big Á Á Ë big big big Ë n e n m n t ˆ 2 Dm solar Dm atm 2 ~ Two mass splittings not very different Atmospheric mixing maximal Any new symmetry or structure behind it?

48 Is There A Structure In Neutrino Masses & Mixings? Monte Carlo random complex 3 3 matrices with seesaw mechanism 5 complex seesaw arbitrary scale sin 2 2q R=Dm 2 solar /Dm2 atm Apparently no particular structure in neutrino mass matrix needed! Anarchy

49 Different Flavor Symmetries Table 3: Order of magnitude predictions for oscillation parameters, from neutrino mass matrices A, SA, H, IH in the text; d 23 denotes the sub-determinant in the 23 sector and we show the effect of its accidental suppression for the semi-anarchical model. In the estimates we have chosen λ = λ. Inverse hierarchy predicts an almost maximal θ 12. Altarelli-Feruglio-Masina hep-ph/ Model parameters d 23 m 2 12/ m 2 23 U e3 tan 2 θ 12 tan 2 θ 23 A b = 0 O(1) O(1) O(1) O(1) O(1) SA b = 1 O(1) O(d 2 23 ) O(λ) O(λ2 /d 2 23 ) O(1) H II a = 1, b = 2 O(λ 2 ) O(λ 4 ) O(λ 2 ) O(1) O(1) H I a = 1, b = 2 0 O(λ 6 ) O(λ 2 ) O(1) O(1) IH O(λ 4 ) O(λ 2 ) O(λ 2 ) 1+O(λ 2 ) O(1) q 13 O(1)? O(l)?(l 2 )? analysis to include also the other models based on SU(5) U(1) 60), which have mass matrix elements defined up to order-one dimensionless coefficients y ij (see eq. 46). For each model, successful points in parameter space are selected by asking that the four observable quantities O 1 = r m 2 12 / m2 23, O 2 = tan 2 θ 12, O 3 = U e3 sin θ 13 sin 2 2q 23 =1.00±0.01? new symmetry

50 Program:More flavor parameters Squarks, sleptons also come with mass matrices Off-diagonal elements violate flavor: suppressed by flavor symmetries M Q 2 ~ M 2 L ~ Ê 1 e e 2 ˆ Á Á e 1 e Á Ë e 2 e 1 Look for flavor violation due to SUSY loops Then look for patterns to identify symmetries Repeat Gell-Mann Okubo! Need to know SUSY masses or TeV-scale physics b R s R g ~ ~ b R ~ s R ~ s R d (d 23 ) RR ~ b R d (d 23 ) RR g ~ s R b R

51 To Figure It Out Models differ in flavor quantum number assignments Need data on q, matter effect, CP 13 violation, B/K-physics, Lepton Flavor Violation, EWSB, proton decay Archaeology We will learn insight on origin of flavor by studying as many fossils as possible cf. CMBR in cosmology

52 Large q 23 and quarks Near-maximal mixing between n t and n m Make it SU(5) GUT Then a large mixing s s R br b R s s R br b R s s R br b R ν ν µ ν ν τ µ µ µ τ τ τ between s and b R R Mixing among righthanded fields drop out from CKM matrix But mixing among superpartners physical O(1) effects on bfis transition possible Expect CP violation in neutrino sector especially if leptogenesis

53 Consequences in B physics b R CP violation in B s mixing (B s fij/y f) b R s R g ~ ~ b R ~ s R ~ s R d (d 23 ) RR ~ b R d (d 23 ) RR g ~ s R b R Addt l CP violation in penguin bfis (B d fif K s ) d (d 23 ) RR ~ ~ b s R R ~ s R B d fix s l + l s _ s s R,L R,L R m~ g (GeV) S fk Excluded by bæsg ~m R3 Dm s (GeV) 400 ps 200 ps Probes if quarks and leptons have common origin of flavor ps

54 Dynamics behind flavor symmetry? Once flavor symmetry structure identified (e.g., Gell-Man Okubo), what is dynamics? (e.g., QCD) Supersymmetry: e Anomalous U(1) gauge symmetry g e L e R with Green-Schwarz mechanism u cm Large Extra Dimensions: Fat brane with physically separated R~100m left- and right-handed particles Technicolor: ETC New broken gauge symmetries at 100TeV scale e L e R

55 Leptogenesis

56 Baryon Asymmetry Early Universe 10,000,000,001 10,000,000,000 q q

57 Baryon Asymmetry Current Universe 1 us q q The Great Annihilation

58 Sakharov s Conditions for Baryogenesis Necessary requirements for baryogenesis: Baryon number violation CP violation Non-equilibrium G(DB>0) > G(DB<0) Possible new consequences in Proton decay CP violation

59 Electroweak Anomaly Actually, SM violates B (but not B L). In Early Universe (T > 200GeV), W/Z are massless and fluctuate in W/Z plasma Energy levels for lefthanded quarks/ leptons fluctuate correspon-dingly DL=DQ=DQ=DQ=DB=1 B=L=0

60 Leptogenesis You generate Lepton Asymmetry first. L gets converted to B via EW anomaly generate L from the direct CP violation in right-handed neutrino decay N 1 h 1j n i H N 1 h * 1k H n k h lj h lk N l n i H e = G(N 1 Æ n i H) - G(N 1 Æ n i H) G(N 1 Æ n i H) + G(N 1 Æ n i H) ~ 1 Im(h 13 h 13 h * 33 h * 33 ) 8p 2 h 13 Two generations enough for CP M 1 M 3 violation because of Majorana nature (choose 1 & 3)

61 Can we prove it experimentally? Unfortunately, no: it is difficult to reconstruct relevant CP-violating phases from neutrino data But: we will probably believe it if 0nbb found CP violation found in neutrino oscillation EW baryogenesis ruled out P (ν µ ν e ) P ( ν µ ν e ) = 16s 12 c 12 s 13 c 2 13 s 23c 23 ( ) ( ) ( m 2 sin δ sin 12 m 2 4E L sin 13 m 2 4E L sin 23 4E L Archeological evidences e.g, B d fif K s )

62 Conclusion

63 Bottomline: Synergy Big questions = ambitious questions Need to clear the cloud of TeV-scale physics to obtain clear views Many different approaches will converge to reveal the big picture Hard, ambitious, but conceivable Expect similar story with ANY scenario of TeV-scale physics

64 Outlook: The Next Twenty Years

65 ...is bright!