Flavor Physics II Brendan Casey, Fermilab CINVESTAV 11/5/2013

Conclusions from yesterday Today: went through the historical progression that leads to our present understanding of flavor physics Next two days: will investigate how this ties into one of the most important scientific questions “Why are we here?” Thursday: will investigate different techniques to predict where to search for new physics B. Casey, 11/5/2013 2/59

Today Electroweak baryogenesis New sources of CP violation –In B physics –In EDMs B. Casey, 11/5/2013 3/59

What was Clinton talking about? It was just this week we had an amazing breakthrough in physics attempting to determine how life began on earth… Subatomic particles of matter, which normally under the laws of physics would be expected to cancel each other out… didn’t because they were slightly more positive than negative He’s correct but slightly out of context B. Casey, 11/5/2013 4/59

Clinton’s talking about here When we study CPV in quarks, we are usually looking here < one billionth of a second old Equal amounts of matter and antimatter Only matter B. Casey, 11/5/2013 5/59

Dirac’s Electron Dirac’s great success was the unification of quantum mechanics and Einstein's relativity. Dirac’s equation predicted new types of electrons. Once you have enough energy, you could produce pairs of these electrons (E=2mc 2 ) New types electrons have opposite charge: anti- electrons or positrons You can create electron-positron pairs, or if you bring an electron and positron together, they annihilate B. Casey, 11/5/2013 6/59

So what's the problem? The problem is how did we get here? If matter and antimatter are created in pairs, where is anti-CINVESTAV? If matter and antimatter annihilate, how did we ever survive 15 billion years or even 15 seconds without all the matter and antimatter canceling out? The fundamental laws of physics are supposed to explain the entire universe, big, small, slow, fast, old and new. But they predict that we shouldn’t exist. B. Casey, 11/5/2013 7/59

Enter Andrei Sakharov Father of the Soviet Hydrogen Bomb Later became a leading human rights activist and received the Nobel Piece Prize in 1975 “a spokesman for the conscience of mankind” In 1967 formulated the ‘Sakharov conditions’ for what needed to happen for the universe as we know it to have formed instead of annihilating itself. B. Casey, 11/5/2013 8/59

Sakharov’s conditions Baryon number violating processes (something that only makes matter or antimatter) B. Casey, 11/5/2013 9/59

Sakharov’s conditions Loss of thermal equilibrium (particles aren't able to communicate with each other) B. Casey, 11/5/ /59

Sakharov’s conditions CP Violation (Harder for antimatter to get through the boundry) Loss of thermal equilibrium (particles aren't able to communicate with each other) Baryon number violating processes (something that only makes matter or antimatter) B. Casey, 11/5/ /59

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Thin film interference B. Casey, 11/5/ /59

Thin film interference B. Casey, 11/5/ /59

Thin film interference B. Casey, 11/5/ /59

Thin film interference B. Casey, 11/5/ /59

There was a boundary in the early life of our universe There was destructive interference in the boundary Some matter waves made it through but antimatter waves didn't B. Casey, 11/5/ /59

What boundary? Main guiding principle of high energy physics is that at high enough energies, everything looks the same This translates into different epochs of time when the universe was at higher and higher temperatures all the way back to the big bang Epochs are characterized by unification of forces The universe comes in phases, just like ice, water, and steam B. Casey, 11/5/ /59

What happens in a phase transition? B. Casey, 11/5/ /59

Our model for how we got here Epochs of time where there were equal amounts of matter and anti-matter There were baryon violating processes but no excess is generated because matter and antimatter excess are in thermal equilibrium The universe begins to go through a phase transition. Our side of the phase starts growing in bubbles. Excesses of matter or antimatter that enter the bubble wall are no longer in thermal equilibrium so they do not necessarily annihilate. There is CP violating interference in the bubble wall that allows a little more matter to get through. This generates the matter asymmetry in the present epoch of the universe. B. Casey, 11/5/ /5 9

Adding it all up at the electroweak scale B. Casey, 11/5/ /59 1: Baryon number violating processes No problem with baryon or lepton violation at high temperature in Standard Model. B-L conserved. Sphaleron transitions shift baryon number into lepton number SU(3)xSU(2)xU(1) Potential energy Total baryon number (or lepton number) B L

Adding it all up at the electroweak scale B. Casey, 11/5/ /5 9 2: Loss of thermal equilibrium Nature of the phase transition can be calculated once all parameters are fixed, including Higgs mass Low Higgs mass (<< 125 GeV) First order transition = bubbles Higgs mass = 125 GeV Second order transition = no bubbles For a SM with m(H) = 125 GeV, no loss of equilibrium. Can not generate a matter asymmetry at the electroweak transition. Conclusion changes if there are new particles at the TeV scale. 1 er order 2 do order

Adding it all up at the electroweak scale B. Casey, 11/5/ /5 9 3: CP Violation Amount of CPV is given by the Jarlskog invariant ~area of the unitarity triangle Even though CKM phase is close to maximal, total effect is small due to small mass differences in first generation and small mixing angles of CKM matrix Can still assume there are new particles at TeV scale and calculate effect: Baryon to photon ratio predicted is 15 orders of magnitude smaller than measured! Need new particles and new CPV or you need to go to a higher phase transition (GUT) Mag(CPV) ≈ f(m 2 j -m 2 i ) × f(  ij ) × sin  CP

CPV in B s mixing 24/5 9 B. Casey, 11/5/2013 (WS Hou)

Dimuon charge asymmetry 25/5 9 B. Casey, 11/5/2013 t W W b s b s t W W b s b s t t B s mixing in the mirror

Measurement history at Dzero 1992: first internal note outlining measurement 1994: 7.3 pb -1 : A = (81-96)/(81+96) 1996: significant asymmetries observed due to asymmetries in range-out. –From then on, Dzero switches polarity every few weeks to enable this measurement 2003: analysis of ~100 pb -1 RunII data indicates we are competitive. Begin planning for a 1 fb -1 result. –Dimuon result. Single muon result ruled out because completely dominated by Kaon asymmetry 26/5 9 B. Casey, 11/5/2013 Iron toroid + -

Measurement history at Dzero 1 fb -1 result: –A SL = -(0.92 ± 0.44 ± 0.32)% –World leading measurement –Dominant error is now Kaon asymmetry determined using D*  D , D  K , K  X Raw asymmetry A = -(0.05± 0.13)% Kaon asymmetry A K = -(0.23 ± 0.08)% 27/59 B. Casey, 11/5/2013

2010 Update Need a way to constrain the Kaon asymmetry Two samples: –Like-sign dimuon system = physics + Kaon –Single muon system: asymmetry is almost entirely from the Kaons Use the single muon system to make a high statistics measurement of the kaon asymmetry and subtract it from the dimuon asymmetry 28/5 9 B. Casey, 11/5/2013

Dimuon results A SL = (0.957±0.251±0.146)% Systematic error dominated by Kaon asymmetry –In dimuon analysis: 2.1% –In combined single and dimuon analysis: 0.15% Verified the B content by measuring the mixing probability in the first fb -1 data set –X = 0.136±0.001±0.024 –PDG: ± /5 9 B. Casey, 11/5/2013

Final results with full dataset B. Casey, 11/5/ /5 9 This is very nice but it is unconfirmed Adding other constraints brings the value closer to the SM

Another source of CPV: EDMs Some EDM PR What is an EDM Why is it important EDM experiments FNAL B. Casey, 11/5/ /59

Nima at the Rockville Meeting B. Casey, 11/5/ /5 9

More Nima B. Casey, 11/5/ /5 9

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Isidori at ichep 2010, EDMs and Flavor B. Casey, 11/5/ /5 9 Large B s CPV shrinks available parameter space Titanium neutron Mercury Buras, Isidori, Paradisi arXiv: B s CPV

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What is an EDM? B. Casey, 11/5/ /59 Classical picture ala Maxwell: There is a fundamental electric charge. There is no fundamental magnetic charge. You have to have a North and South pole. Non-relativistic quantum mechanics ala Pauli: There is an electric charge that couples to the scalar field There is a magnetic spin that couples to the vector field. Classical to Quantum: charge goes to charge, North-South goes to Up-Down

Classical to quantum B. Casey, 11/5/ / Magnetic dipole Electric monopole + + Electric dipole Classical extended objects Point particles with quantum numbers that have classical analogies

What is an EDM? B. Casey, 11/5/ /5 9 Dirac’s electron: There is a fundamental degree of freedom associated with spin –Even though the electron is a point particle There is a new fundamental degree of freedom: antimatter –Dirac tried to explain this away using hole theory as simply the absence of charge. But his equation was right and he was wrong. There is a new fundamental degree of freedom: ‘electric spin’ …and it’s imaginary! –Dirac dismissed this because it was pure imaginary. –Is this another case where Dirac’s equation was right and he was wrong?

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Imaginary charge Quantum imaginary charges are very important –They flip sign when you do a CP transformation, i.e. they violate CP –It is OK to be imaginary because we only measure their absolute value, but the interference they cause has measurable effects Question: What is the only particle we’ve discovered that seems to have intrinsic imaginary charge? – Disclaimer: Theorists would say this is arbitrary but that’s not fun. B. Casey, 11/5/ /59

Imaginary charge Answer: the top quark B. Casey, 11/5/ /5 9 t d W Top quark is responsible for all the CP violation we see in B and K mixing. –With the exception of our dimuon asymmetry OK, the b quark also has the same imaginary charge as the top. (same  ) –With the exception of the K  problem  –  i  t t s s d d W W t t b b d d W W b W u  –  i 

QCD’s EDM Here is a list of facts I haven't figured out yet: –Also turns out that QCD predicts an electric dipole moment for QCD objects –This naturally falls out of the QCD Lagrangian –The lack of EDMs is the ‘strong CP problem’ –You can cancel this term in the QCD Lagrangian with an Axion. –This also ties the question of EDMs to dark matter. B. Casey, 11/5/ /5 9

What do EDMs look like? It can be a fundamental parameter just like spin and charge –Dirac’s EDM or QCD’s EDM ( e-cm) It can be something that couples to an electric field like an EDM would –Remember, spin is called spin because of the way electrons behave in a magnetic field B. Casey, 11/5/ /5 9 Electron EDM generated by CKM e-cm Neutron EDM generated by CKM e-cm (Klaus Kirch)

What do EDMs look like? Since we are talking about loops, anything goes –This is where the new physics comes in B. Casey, 11/5/ /5 9 For leptons: –Dirac EDM + CKM EDM –NP loops For nucleons and atoms: –Dirac EDM+QCD EDM+CKM EDM –NP interactions quark + loops (same as lepton) quark-quark quark-gluon nucleon-nucleon –This is complicated. But the take away message is you need several systems to interpret the limits. >N measurements for N sources of EDMs Not just about the best EDM limit (Michael Ramsey-Musolf)

Great, but why do we care? (I) We know we need new sources of CPV. –Flavor changing processes can’t generate enough matter But two anomalies are not yet understood –Our dimuons and the K  problem –B d has large SM background, B s doesn’t That’s why we searched there and that’s why we interpret our result as new physics –What if the new CPV is not flavor changing? B and K physics tell us nothing Would show up in EDMs –Particle’s magnetic moment has large SM background, particle’s EDM doesn’t Same smoking gun argument B. Casey, 11/5/ /5 9

Neutral system Experiments B. Casey, 11/5/ /59 Trap neutral system. Flip the E field and subtract the results. Main background (magnetic precession) cancels. Then spend a lifetime understanding the systematics (Kirch)

Charged particle systems B. Casey, 11/5/ /5 9 problem: cant trap a charged particle solution: can store a charged particle. Look and see if things are still aligned when the particle comes back around again Are different ways of canceling out the main magnetic precession term and systematics. State-of-the-art is muon g-2 +

Results B. Casey, 11/5/ /5 9

Some details Hg limit is but proton limit is only , why? B. Casey, 11/5/ / External E field internal E field Particles see a much smaller field

The right atoms Need atoms with weird shapes so everything won’t cancel –Octopole deformation Mercury is the best stable atom for this But there are even better atoms and isotopes that are unstable B. Casey, 11/5/ /59

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More details Fundamentally table top experiments –Order $1M Next gen neutron EDM –Order $100M for experiment –Order $1B if you also need a new spallation source Another problem –Spallation sources are designed as user facilities for material science –Not well matched to doing fundamental precision neutron science at the level B. Casey, 11/5/ /5 9

Project X Have an opportunity to make a spallation source tailored to the needs of ultra-precision neutron experiments –This community is very interested Plus: B. Casey, 11/5/ /5 9

Proton EDM We can put the proton EDM ring in the accumulator –This needs a very small fraction of the beam we already have. –Don’t even need Project X B. Casey, 11/5/ /5 9

Where are we? Have a enormous program to look for new TeV particles at the LHC Have a broad program at Belle II and LHC to search for new CPV in flavor changing processes Have a broad program around the word to search for CPV in flavor conserving processes B. Casey, 11/5/ /59

What this might look like B. Casey, 11/5/ /5 9 Have the ability to confirm, seriously constrain, or possibly rule out electoweak baryogenesis as the source of the matter asymmetry in the universe with existing experiments or ones under construction

Conclusions for today Flavor physics is tied to one of the most important questions in science today –Why are we here? Leading theory is electroweak baryogenesis –Lack of new CPV, large Higgs mass, and no new particles at the LHC make this difficult to work Next step is to explore how this would work at the next phase transition –GUT scale B. Casey, 11/5/ /5 9