arXiv subjects

Robert Knegjens

Publications and source records attributed to Robert Knegjens.

22 records · Page 2Linked to original sources

arXiv2011

Anatomy of $B^0_{s,d} \to J/ψf_0(980)$

The $B^0_s\to J/ψf_0(980)$ decay offers an interesting experimental alternative to the well-known $B^0_s\to J/ψϕ$ channel for the search of CP-violating New-Physics contributions to $B^0_s$--$\bar B^0_s$ mixing. As the hadronic structure of the $f_0(980)$ has not yet been settled, we take a critical look at the implications for the relevant observables and address recent experimental data. It turns out that the effective lifetime of $B^0_s\to J/ψf_0(980)$ and its mixing-induced CP asymmetry $S$ are quite robust with respect to hadronic effects and thereby allow us to search for a large CP-violating $B^0_s$--$\bar B^0_s$ mixing phase $ϕ_s$, which is tiny in the Standard Model. However, should small CP violation, i.e. in the range $-0.1\lsim S\lsim 0$, be found in $B^0_s\to J/ψf_0(980)$, it will be crucial to constrain hadronic corrections in order to distinguish possible New-Physics effects from the Standard Model. We point out that $B^0_d\to J/ψf_0(980)$, which has not yet been measured, is a key channel in this respect and discuss the physics potential of this decay.

hep-ph↗

arXiv2010

A Fresh Look at B_{s,d} -> pi pi, pi K, K K Decays

Using updated measurements and SU(3)-breaking form factors, we have a detailed look at the B_d -> pi^+ pi^-, B_s -> K^+ K^- and B_d -> pi^\mp K^\pm, B_s -> pi^\pm K^\mp systems. The corresponding decays are related to each other by the U-spin symmetry of strong interactions and offer determinations of the angle gamma of the unitarity triangle. In the former case, we obtain gamma=(68.3^{+4.8}_{-5.7}^{+5.0}_{-3.7}) deg, which is in excellent agreement with the Standard-Model fits of the unitarity triangle. The first errors correspond to experimental input uncertainties, while the latter are an estimate of U-spin-breaking effects. In view of this result, large CP-violating new-physics effects at the amplitude level are excluded. However, the effective B_s -> K^+ K^- lifetime and the mixing-induced CP violation in this channel offer interesting probes for New Physics in B^0_s-\bar B^0_s mixing. In the case of the B_d -> π^\mp K^\pm, B_s -> pi^\pm K^\mp system, using additional information from B^\pm -> π^\pm K, we obtain a bound of gamma \leq (71.8^{+5.4}_{-4.3}) deg, and the range 24 deg \leq gamma \leq 71 deg. We perform also tests of the U-spin symmetry and do not find any indication for large non-factorizable corrections.

hep-ph↗

arXiv2010

In Pursuit of New Physics with B^0_s -> K^+K^-

The B^0_s -> K^+K^- decay is the U-spin partner of B^0_d -> pi^+π^- and allows a determination of the angle gamma of the unitarity triangle of the Cabibbo-Kobayashi-Maskawa matrix. Using updated information on the branching ratio and the relevant hadronic form factors, we discuss the picture that emerges for gamma from the currently available data, which is in good agreement with the fits of the unitarity triangle. We point out that the B^0_s -> K^+K^- decay also offers interesting probes to search for new physics in B^0_s-\bar B^0_s mixing, thereby complementing the well-known B^0_s -> J/psi phi analyses. The relevant observables are the effective lifetime of this channel and its mixing-induced CP asymmetry. We calculate correlations between these quantities and the CP-violating B^0_s-\bar B^0_s mixing phase, which serve as target regions for improved measurements at the Tevatron and the early data taking at the LHCb experiment. Finally, we discuss the expected situation for the optimal determination of gamma at LHCb, exploiting precise measurements of the CP violation in B^0_s -> K^+K^-.

hep-ph↗

arXiv2010

Single top production in a non-minimal supersymmetric model

We study single top production at the LHC in a SUSY-QCD model with a heavy Dirac gluino. The presence of a heavy Dirac gluino allows for notable top-up flavour changing neutral currents. In this scenario, we find that the process ug->tg gives the largest contribution to single top production via FCNCs at the LHC. The key features of this signal are that the top quark is produced very forward and that it is asymmetric to its anti-top counterpart, as the latter lacks a valence quark.

hep-ph↗