Roman Zwicky Institute for Particle Physics Phenomenology Department of Physics University of Durham Science Laboratories South Rd Durham DH1 3LE UNITED KINGDOM Tel: +44-(0)191-334-3776 (direct) Tel: +44-(0)191-334-3811 (IPPP Office) Fax: +44-(0)191-334-3658 (IPPP Office) E-mail: user: Roman.Zwicky, domain: durham.ac.uk

Publications

Listing from SLAC-SPIRES

Research Areas

• Phenomenology
• Formal aspects of Quantum Field Theory

Research Interests

Flavour Physics:

1. Meson Distribution Amplitudes: DA are objects translating hadrons into quarks and gluons. They are defined around the light cone and are therefore relevant in exclusive decays with high momentum transfer e.g. B \to \pi (l\nu). We have derived some constraints on pion distribution amplitude from the Babar-spectrum of B \to pi(l\nu) (hep-ph/0507076) and constraints on the Kaon distribution amplitudes (a_1 first Gegenbauer moment) (hep-ph/0510338) (hep-ph/0601086)
2. B to meson formfactors: We have calculated the formfactors from B_(d,s) meson to the light pseudoscalars \pi,K,.. and the vector mesons \rho.K^* ... within the framework of Light-Cone Sum Rules. The LCSR allow an analytic treatment of the formfactors up to q2 < 14GeV2. The the pseudoscalars various lattice QCD groups allow to extract the formfactor for q2 > 16GeV2 and are therefore complementary to LCSR> There are currently no unquenched calculations available for vector mesons because for light quark masses the vector meson are unstable particles. The formfactors for V-A currents are typically used to extract observables in tree level processes whereas penguin current formfactors appear in rare decays and therefore play an important role in indirect searches of new physics. (hep-ph/0110115) (hep-ph/0406232) (hep-ph/0406261) (hep-ph/0412079)
3. |V_ub|_excl: The formfactor f_+(B \to pi) directly enters the decay rate for B \to pi(l\nu) and can be directly used to extract the CKM-matrix element |V_ub|. We have used the 5 Babar bins from 2005 to extract |V_ub| with a 13% uncertainty. (hep-ph/0507076) (HFAG)
4. |V_cb|_incl : We have worked on the extraction of |V_cb| from the inclusive channel. The approach uses the Wilsonian OPE with the renormalon free kinetic mass. We have calculated 1/mb^3 effects due to the charm in the B-meson. We found a curious Coulomb enhancement and cancellations between electric and magnetic parts and we have estimated matrix elements of the type B|bE2b|B and therefore extended the heavy quark expansion. (hep-ph/0511158)
5. |V_td/V_ts|_excl : Contrary to |V_ub| and |V_cb| the CKM fraction |V_td/V_ts| is not a tree level quantity and therefore sensitive to new physics. It has been suggested a long time ago that |V_td/V_ts| can be extracted from the ratio of decay amplitudes B-> rho gamma over B -> K* gamma. Even more due to accidental CKM suppression (alpha \sim 90) the power corrections are suppressed as well and the whole operation is even under better control. The very rare decay B-> rho gamma has been observed by Belle in 2005 and BaBar 2006. Our calculation of the decay ratio and extraction of |V_td/V_ts| can be found (hep-ph/063232) and a shorter and less technical write up is found in the procceedings to QAQCD 06 (hep-ph/0608009)
6. S_K*gamma S_K*gamma is the time dependent CP asymmetry of B -> K* gamma. In 97 it was noticed that the standard model (V-A interaction !) produces mainly left handed photons in \bar B -> \bar K* gamma_L(R), O(m_s/m_b). A non-vanishing time dependent CP-asymmetry demands both chiralities and is therefore very small \sim -2%. It was noticed that gluon emission from c and u-loops produce both chiralities and it was guestimated to give a contribution of -10% (hep-ph/0412019) plus a large uncertainty. We have performed a straightforward calculation and have shown that the contribution is 0.5% \pm 1% ! (hep-ph/0609037) and therefore S_K*gamma etc remain important (quasi) null tests of the standard model. The current HFAG value is S_K*gamma = -28 \pm 26 % ! All TDCP asymmetries for B-> V gamma are observables of primary interest for the SuperB-factory.

Formal Aspects:

1. Non-commutative field theory: Is a quantum field theory implementing the coordinate commutator [x_\mu,x_\nu] = \theta_\mu\nu which is motivated from black-hole thought experiments and certain string theory backgrounds. In most attempts \theta_\mu\nu is chosen to be a constant tensor. I have worked on the causality and unitarity properties of these field theories. According to my knowledge it is still unknown how to take the field theory limit theta_\mu\nu \to 0 because of the so-called UV-IR problem. (hep-th/0103069)
2. Central charge anomalies: It is well known that central charges in the supersymmetry algebra give lower bounds on mass-spectrum. The bound is saturated by BPS-solitons. When Witten discovered that CP(N) models exhibit BPS-solitons in the large N limit he conjectured anomalous central charges in the superalgebra. In our work we calculate the anomalous charge in various ways and identify the anomalous charge as a part of the supermultiplet of anomalies (chiral,conformal,scale). (hep-th/0602004)

Some recent talks

• November 2005: Durham IPPP-seminar : CKM-matrix -- non-perturbative charm in |V_{cb}|_incl
• January 2006: Babar-Belle Workshop (Melbourne): B to \pi formfactor from Light-Cone Sum Rules
• February 2006: Flavour Physics in the LHC Era (Cern): B meson formfactors and recent progress on the Kaon Distribution Amplitude
• February 2006: Euridice Collaboration Meeting (Marseille): Recent progress on the Kaon Distribution Amplitude
• April 2006: UK Super-B meeting (Daresbury-Lab): Two Aspects of current CKM - relevance for Super-B
• May 2006: Continuous advances in QCD (Minneapolis): B -> K* gamma vs B -> rho gamma
• June 2006: Weekly Seminar (Southampton): CKM - Kaon Distribution Amplitude - Rare decays B -> V gamma
• September 2006: Workshop Distribution Amplitudes (Durham): Twist-2 from QCD sum rules
  
• October 2006: Flavour Physics in the LHC Era (Cern): |V_td/V_ts| from B-> V gamma and TDCP asymmetry as a (quasi) null test of the standard model
  
• December 2006: B physis -- B->Vgamma beyond QCD factorization (Durham):
  
• December 2006: Weekly Seminar Glasgow B->V gamma beyond QCD factorization

Current Projects

• Power corrections (annhilation, u-loop and c-loop) to B -> V gamma, important for B -> rho gamma, Isospin breaking in B-> V gamma etc

Exercises composed for blockcourse on Quantum Field Theory at ETH Zurich & University of Zurich 2003

• Exercises (informal style) PDF-file