Narrow Results

With the LHC Run 1 data, the LHCb experiment discovered two pentaquark states and has evidence for a number of possible anomalies in the flavour sector. The possible anomalies include indications of violations of lepton flavour universality, deviations from Standard Model predictions in several $B$-meson decay modes that are mediated by flavour-changing neutral currents, and further evidence for a discrepancy between inclusive and exclusive measurements of the CKM matrix element $\left|V_{ub}\right|$.

Experimental era of rare $B$-decays started with the measurement of $B\to K^{\ast }\gamma$ by CLEO in 1993, followed by the measurement of the inclusive decay $B\to X_s\gamma$ in 1995, which serves as the standard candle in this field. The frontier has moved in the meanwhile to the experiments at the LHC, in particular, LHCb, with the decay $B^0\to {\mu }^{+}{\mu }^{-}$ at about 1 part in 10${}^{10}$ being the smallest branching fraction measured so far. Experimental precision achieved in this area has put the standard model to unprecedented stringent tests and more are in the offing in the near future. I review some key measurements in radiative, semileptonic and leptonic rare $B$-decays, contrast them with their estimates in the SM, and focus on several mismatches reported recently. They are too numerous to be ignored, yet, standing alone, none of them is significant enough to warrant the breakdown of the SM. Rare $B$-decays find themselves at the crossroads, possibly pointing to new horizons, but quite likely requiring an improved theoretical description in the context of the SM. An independent precision experiment such as Belle II may help greatly in clearing some of the current experimental issues.

The charge given to me by the organisers of the memorial meeting for Prof. Abdus Salam’s 90th birthday is to recall my personal impressions of him and review an aspect of the standard model (SM) physics related to my work. Salam was, first and foremost, a brilliant theoretical physicist whose work is still very much en vogue, currently being tested precisely by the experiments at the Large Hadron Collider (LHC). Salam was, however, equally effective as a scientific advisor to many institutions, such as IAEA and CERN, but also to the government of Pakistan as the chief scientific strategist. He was also an untiring advocate of scientific research and higher education in developing countries, which took a concrete form in the International Centre for Theoretical Physics (ICTP) in Trieste. I discuss these aspects of his scientific life seen from my perspective in the first part. In the second part of my talk, which may appear as a disjoint piece to the first, I summarise some selected topics in rare B-decays — the current flavour physics frontier. Experiments carried out over several decades are largely in agreement with the SM, thanks also to dedicated theoretical effort in their interpretation. However, this field is undergoing an anomalous phase in a number of key measurements, in particular reported by LHCb, triggering a very lively debate and model building. These anomalies, which I review here, are too numerous to be ignored, but none is individually significant enough to announce a breakdown of the SM.

The KLOE experiment at the Frascati e⁺e⁻ collider DAΦNE, operating at the ϕ peak, provides unique opportunities for precision measurements of kaon branching ratios. We present the upper limit on the branching ratio of the CP violating decay K_S → 3π⁰ obtained with 1.7 fb^-1 of e⁺e⁻ collisions collected by the KLOE detector. We also present the new preliminary result of the branching ratio for K⁺ → π⁺π⁻π⁺(γ) using approximately 10% of all KLOE data.

The NA48/2 and NA62 collaborations report on recent results, current status, and prospects of kaon physics at the CERN-SPS. The NA62 collaborations aims to measure the decay $K^{\pm }\to {\pi }^{\pm }\nu \bar{\nu }$ with an uncertainty of 10% or better. The NA62 detector and preliminary results from a pilot run in 2014 are presented. In addition, recent results of the NA48/2 collaboration are reported. A search for Dark Photons has been performed in ${\pi }^0$ decays via the kaon decays $K^{\pm }\to {\pi }^{\pm }{\pi }^0$ and $K^{\pm }{\pi }^0{\mu }^{\pm }\nu$. No dark photon signal was observed and new upper limits on the mixing parameter ${ϵ}^2$ and the dark photon mass were computed. We also report the first observation of the kaon decay $K^{\pm }\to {\pi }^{\pm }{\pi }^0{e}^{+}{e}^{-}$.

Measurements of CP-violating observables in B meson decays can be used to determine the angles of the Unitarity Triangle and hence probe for manifestations of New Physics beyond the Cabibbo-Kobayashi-Maskawa Standard Model paradigm. Of particular interest are precise measurements of the angles γ and β. Also of great importance are studies of CP-violation involving $B_s^0$ mesons, in particular the phase ϕ_s, which is a golden observable in flavour physics at the LHC. Complementary to these studies is the continuing search for direct and indirect CP-violation in the charm system, where the experimental precision is now at the 10⁻³ level. I will present new and recent results in these topics, and in CP-violation searches in baryon decays, with specific emphasis on the measurement programme at the LHC.

Recent work on adding flavor to the generalized AdS/CFT correspondence is reviewed. In particular, we consider instanton configurations on two coincident D7 brane probes. These are matched to the Higgs branch of the dual field theory. In AdS₅ × S⁵, the instanton generates a flow of the meson spectrum. For non-supersymmetric gravity backgrounds, the Higgs branch is lifted by a potential, which has non-trivial physical implications. In particular these configurations provide a gravity dual description of Bose-Einstein condensation and of a thermal phase transition.

The charge given to me by the organisers of the memorial meeting for Prof. Abdus Salam’s 90th birthday is to recall my personal impressions of him and review an aspect of the standard model (SM) physics related to my work. Salam was, first and foremost, a brilliant theoretical physicist whose work is still very much en vogue, currently being tested precisely by the experiments at the Large Hadron Collider (LHC). Salam was, however, equally effective as a scientific advisor to many institutions, such as IAEA and CERN, but also to the government of Pakistan as the chief scientific strategist. He was also an untiring advocate of scientific research and higher education in developing countries, which took a concrete form in the International Centre for Theoretical Physics (ICTP) in Trieste. I discuss these aspects of his scientific life seen from my perspective in the first part. In the second part of my talk, which may appear as a disjoint piece to the first, I summarise some selected topics in rare B-decays — the current flavour physics frontier. Experiments carried out over several decades are largely in agreement with the SM, thanks also to dedicated theoretical effort in their interpretation. However, this field is undergoing an anomalous phase in a number of key measurements, in particular reported by LHCb, triggering a very lively debate and model building. These anomalies, which I review here, are too numerous to be ignored, but none is individually significant enough to announce a breakdown of the SM.

With the LHC Run 1 data, the LHCb experiment discovered two pentaquark states and has evidence for a number of possible anomalies in the avour sector. The possible anomalies include indications of violations of lepton avour universality, deviations from Standard Model predictions in several B-meson decay modes that are mediated by avour-changing neutral currents, and further evidence for a discrepancy between inclusive and exclusive measurements of the CKM matrix element |V_ub|.

Experimental era of rare B-decays started with the measurement of B → K^*γ by CLEO in 1993, followed by the measurement of the inclusive decay B → X_sγ in 1995, which serves as the standard candle in this field. The frontier has moved in the meanwhile to the experiments at the LHC, in particular, LHCb, with the decay B⁰ → μ⁺μ⁻ at about 1 part in 1010 being the smallest branching fraction measured so far. Experimental precision achieved in this area has put the standard model to unprecedented stringent tests and more are in the offing in the near future. I review some key measurements in radiative, semileptonic and leptonic rare B-decays, contrast them with their estimates in the SM, and focus on several mismatches reported recently. They are too numerous to be ignored, yet, standing alone, none of them is significant enough to warrant the breakdown of the SM. Rare B-decays find themselves at the crossroads, possibly pointing to new horizons, but quite likely requiring an improved theoretical description in the context of the SM. An independent precision experiment such as Belle II may help greatly in clearing some of the current experimental issues.

We have investigated a flavour model which inspired by small squared-mass difference measured in solar neutrino oscillation experiments and observability in neutrinoless double beta decay experiments. In our model, the 1^st. and 2^nd. generations of fermions have a common mass at the leading order. Such limit may be a good starting point from the points of view of understanding the mixing patterns and mass spectra. In this limit, the mass matrices are respected an O(2) symmetry on flavor space of the first two generations. For simplicity, we propose a model for lepton sector based on the D_N group which is a discrete subgroup of O(2). We show that our model can reproduce the experimental data without hierarchical couplings except for 5–10% tuning partially for the large neutrino mixing. Further, we show a novel relation between the tiny electron mass and the relatively large θ^PMNS₁₃ via CP violation by the complex vacuum expectation values of the extra scalar fields.

This article contains a summary of results obtained by the LHCb experiment at CERN concerning CP violation and rare decays of b quarks, obtained from 7-8 TeV pp collisions at the LHC. Particular attention is given to recent constraints to new physics beyond the Standard Model, derived from observations of precision observables involving leptonic final states. These include dimuon decays of B-mesons, b → sμ⁺μ⁻ transitions, and first precision measurements of the CKM matrix phases β_s and γ.