Perspectives in charm physics: theory Alexey A. Petrov Wayne State University Michigan Center for Theoretical Physics Table of Contents: • Introduction • Charm as QCD laboratory • Charm as New Physics laboratory • Conclusions Alexey A Petrov (WSU & MCTP) Intensity Frontier Workshop, ANL 25-27 April 2013 Thursday, April 25, 13
"It's Hard To Make Predictions, Especially About the Future" Yogi Berra, Neils Bohr or Mark Twain Alexey A Petrov (WSU & MCTP) Intensity Frontier Workshop, ANL 25-27 April 2013 36 Thursday, April 25, 13
"It's Hard To Make Predictions, Especially About the Future" Yogi Berra, Neils Bohr or Mark Twain "If You Don't Think About The Future, You Cannot Have One." John Golsworthy (1932 Nobel Prize in Literature) Alexey A Petrov (WSU & MCTP) Intensity Frontier Workshop, ANL 25-27 April 2013 36 Thursday, April 25, 13
1. Introduction: energy scales ★ Main goal of the exercise: understand physics at the most fundamental scale ★ It is important to understand relevant energy scales for the problem at hand physics of beauty physics of charm m t m W t b,s,d c,u m b s,d b c,u t m c b s,d dominant dominant small small Alexey A Petrov (WSU & MCTP) Intensity Frontier Workshop, ANL 25-27 April 2013 35 Thursday, April 25, 13
Introduction: charm ★ Modern approach to flavor physics calculations: effective field theories ★ It is important to understand relevant energy scales for the problem at hand Physics at 10 n TeV scale Reach Charm physics Non-perturbative Quarkonia Heavy ions Lattice QCD QCD and exotics Breadth Alexey A Petrov (WSU & MCTP) Intensity Frontier Workshop, ANL 25-27 April 2013 34 Thursday, April 25, 13
Introduction: charm ★ Modern approach to flavor physics calculations: effective field theories ★ It is important to understand relevant energy scales for the problem at hand Physics at 10 n TeV scale Reach Charm physics Non-perturbative Quarkonia Heavy ions Lattice QCD QCD and exotics Breadth Alexey A Petrov (WSU & MCTP) Intensity Frontier Workshop, ANL 25-27 April 2013 34 Thursday, April 25, 13
Breadth: QCD Alexey A Petrov (WSU & MCTP) Intensity Frontier Workshop, ANL 25-27 April 2013 Thursday, April 25, 13
2a. Inclusive Decays and Lifetimes 1. Nice test of our understanding of non-perturbative effects in QCD 2. One of the few unambiguous theoretical predictions that are easy to test experimentally 3. Theoretical uncertainty can be estimated: precision studies How good are theoretical predictions? Alexey A Petrov (WSU & MCTP) Intensity Frontier Workshop, ANL 25-27 April 2013 33 Thursday, April 25, 13
2b. Leptonic decays of D + and D s ★ In the Standard Model probes meson decay constant/CKM matrix element � 0 | s γ µ γ 5 c | D s ⇥ = if D s p µ D s ⇥ 2 � Γ ( D q → ⌥� ) = G 2 1 − m 2 | V cq | 2 ⇤ 8 ⇥ f 2 F D q m 2 ⇤ M D q M 2 D q … so theory can be compared to experiment by comparing |f Dq V cq | see Artuso, Meadows, AAP ★ New physics contribution to D s → l ν decay - possible heavy NP mediators Akeryod; Hou; Hewett Dobrescu, Kronfeld see Dorsner, Fajfer, Kamenik and Kosnik Aditya, Healey, AAP - ultra-light NP particle emission in the final state? No helicity suppression !!! No discrepancy between theory and experiment J. Shigemitsu, CKM-2010 Alexey A Petrov (WSU & MCTP) Intensity Frontier Workshop, ANL 25-27 April 2013 32 Thursday, April 25, 13
Radiative leptonic decays of D + and D s ★ Recall that purely leptonic decays are helicity suppressed in the SM - add photon to the final state to lift helicity suppression � d 4 xe − ikx ⇥ ∗ α β ⌅ 0 | T [ J em A ( D ⇥ µ ¯ ⌅� ) = ⌅ µ ¯ ⌅� ( k ) | H w (0) | D ( p ) ⇧ � α ( x ) J β (0)] | D ( p ) ⇧ LSZ reduction + e/m perturbation theory ⇥ 2 � m D D = Γ ( D → ⌦⌅⇥ ) Γ ( D → ⌦⌅ ) = � ★ Define R ⇤ µ 2 V I ( ∆ , m D , ⇥ i ) 6 ⇧ m ⇤ Burdman, Goldman, Wyler ★ Estimate - results in B(D → µ νγ ) ~ 10 -5 and B(D s → µ νγ ) ~ 10 -4 with B(D → e νγ ) >> B(D → e ν ) - for B-mesons, QCD-based calculations are possible Lunghi, Pirjol, Wyler Korchemsky, Prjol, Yan ★ Is lattice prediction for D → µ νγ possible? - charmonium radiative decays Dudek, Edwards; Dudek, Edwards, Roberts - photon structure functions, pion form-factor, etc. X. Ji, C. Jung Alexey A Petrov (WSU & MCTP) Intensity Frontier Workshop, ANL 25-27 April 2013 31 Thursday, April 25, 13
2c. Semileptonic decays of D-mesons ★ In the Standard Model probes meson form factor/CKM matrix element - direct access to V cs and V cd - lattice QCD: exclusive transitions ★ Decay rate depend on form factors - parameterization of q 2 dependence defines a model where ★ Can success of LQCD calculations of D → K and D → π form factors be replicated for other systems? - calculations of D s form factors - calculations of semileptonic decays of baryons Alexey A Petrov (WSU & MCTP) Intensity Frontier Workshop, ANL 25-27 April 2013 30 Thursday, April 25, 13
2d. Quarkonia and exotics ★ Rich physics opportunities for studies of QCD in different regimes - effective theories for charmonium states - charmonium exotics - lattice QCD: exclusive transitions 2e. Charm in heavy ion collisions ★ Rich physics opportunities for studies of QCD in different regimes - charmonium suppression - do charm quarks flow? - how do charm quarks loose energy while propagating through a QGP (radiative vs. collisional energy loss)? - how do charm quarks hadronize in a decaying QGP (recombination vs. fragmentation)? - what are the charm quark transport coefficients (e.g. diffusion constant)? - what QGP properties are charm quarks most sensitive to? Alexey A Petrov (WSU & MCTP) Intensity Frontier Workshop, ANL 25-27 April 2013 29 Thursday, April 25, 13
Reach: MIXING Alexey A Petrov (WSU & MCTP) Intensity Frontier Workshop, ANL 25-27 April 2013 Thursday, April 25, 13
3a. Mixing: short vs long distance ★ How can one tell that a process is dominated by long-distance or short-distance? ★ To start thing off, mass and lifetime differences of mass eigenstates... x D = M 2 − M 1 , y D = Γ 2 − Γ 1 Γ D 2 Γ D ★ ...can be calculated as real and imaginary parts of a correlation function 1 Z n o d 4 x T H | ∆ C | =1 ( x ) H | ∆ C | =1 | D 0 i Im h D 0 | i y D = (0) w w 2 M D Γ D bi-local time-ordered product 1 � Z 2 h D 0 | H | ∆ C | =2 | D 0 i + h D 0 | i n o H | ∆ C | =1 ( x ) H | ∆ C | =1 d 4 x T | D 0 i x D = Re (0) w w 2 M D Γ D bi-local time-ordered product local operator (b-quark, NP): small? ★ So, the big question is if the integrals are dominated by x → 0 ??? Alexey A Petrov (WSU & MCTP) Intensity Frontier Workshop, ANL 25-27 April 2013 28 Thursday, April 25, 13
Mixing: short vs long distance ★ How can one tell that a process is dominated by long-distance or short-distance? ★ It is important to remember that the expansion parameter is 1/E released 1 Z n o d 4 x T H | ∆ C | =1 ( x ) H | ∆ C | =1 | D 0 i Im h D 0 | i y D = (0) w w 2 M D Γ D OPE-leading contribution: ★ In the heavy-quark limit m c → ∞ we have m c ≫ ∑ m intermediate quarks , so E released ~ m c - the situation is similar to B-physics, where it is “short-distance” dominated - one can consistently compute pQCD and 1/m corrections ★ But wait, m c is NOT infinitely large! What happens for finite m c ??? - how is large momentum routed in the diagrams? - are there important hadronization (threshold) effects? Alexey A Petrov (WSU & MCTP) Intensity Frontier Workshop, ANL 25-27 April 2013 27 Thursday, April 25, 13
Mixing: Standard Model predictions ★ Predictions of x and y in the SM are complicated x D = M 2 − M 1 , y D = Γ 2 − Γ 1 - second order in flavor SU(3) breaking Γ D 2 Γ D - m c is not quite large enough for OPE * - x, y << 10 -3 (“short-distance”) - x, y ~ 10 -2 (“long-distance”) ★ Short distance: - assume m c is large - combined m s , 1/m c , a s expansions - leading order: m s2 , 1/m c6 ! - threshold effects? H. Georgi; T. Ohl, … I. Bigi, N. Uraltsev; M. Bobrowski et al ★ Long distance: - assume m c is NOT large - sum of large numbers with alternating signs, SU(3) forces zero! - multiparticle intermediate states * Not an actual representation of theoretical uncertainties. Objects might be bigger then dominate J. Donoghue et. al. what they appear to be... P. Colangelo et. al. x = 0.63 +0.19-0.20 % Falk, Grossman, Ligeti, Nir. A.A.P. Phys.Rev. D69, 114021, 2004 y = 0.75 ± 0.12 % Falk, Grossman, Ligeti, and A.A.P. Phys.Rev. D65, 054034, 2002 HFAG 2012 Alexey A Petrov (WSU & MCTP) Intensity Frontier Workshop, ANL 25-27 April 2013 26 Thursday, April 25, 13
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