arXiv subjects

Ignacio Bediaga

Publications and source records attributed to Ignacio Bediaga.

At least 19 recordsLinked to original sources

arXiv2023

Enhanced charm CP asymmetries from final state interactions

We show that final state interactions (FSI) within a CPT invariant two-channel framework can enhance the charge-parity (CP) violation difference between $D^0\toπ^-π^+$ and $D^0\to K^-K^+$ decays up to the current experimental value. This result relies upon: (i) the dominant tree level diagram, (ii) the well-known experimental values for the $D^ 0\toπ^-π^+$ and $D^ 0\to K^-K^+$ branching ratios, and (iii) the $ππ\to ππ$ and $ππ\to K K $ scattering data to extract the strong phase difference and inelasticity. Based on well-grounded theoretical properties, we find the sign and bulk value of the $ΔA_{CP}$ and $A_{CP}(D^0 \to π^-π^+)$ recently observed by the LHCb Collaboration.

hep-ph↗

arXiv2022

Global CP asymmetries in charmless three-body $B$ decays with final state interactions

We propose a theoretical framework to understand the observable charge-parity (CP) violation in charmless three-body $B^\pm$ decays. The decay amplitudes put together the $ππ\to KK $ re-scattering and the U-spin symmetry, treated within a CPT invariant framework. This approach applied to a two-channel model provides the magnitudes and signs of the ratios of the global CP asymmetries for $B^\pm \to K^\pm π^+ π^- \,$, $B^\pm \to K^\pm K^+ K^- \,$, $B^\pm \to π^\pm K^+ K^- \,$ and $B^\pm \to π^\pm π^+π^- \,$ decays, compatible with those obtained from the available experimental data. In addition, by considering the neutral channels we predict the ratios for the global CP asymmetries for these decays.

hep-ph↗

arXiv2020

Direct CP violation in beauty and charm hadron decays

Since the discovery of CP violation more than 5 decades ago, this phenomenon is still attracting a lot of interest. Among the many fascinating aspects of this subject, this review is dedicated to direct CP violation in non-leptonic decays. The advances within the last decade have been enormous, driven by the increasingly large samples of b- and c-hadron decays, and have led to very interesting results such as large CP asymmetries in charmless B decays and the observation of direct CP violation in the charm sector. We address the quest for understanding the origin of strong phases, the importance of final state interactions and the relation with CPT symmetry, and different approaches to measure direct CP violation in these decays. The main experimental results and their implications are then discussed.

hep-ex↗

arXiv2019

Gravitational baryogenesis without CPT violation

We show that in theories with nonminimal curvature-matter couplings up to first order in the curvature, baryon number (B) conservation and CP are automatically violated, provided that the curvature scalar and its gradient do not vanish. Together with the associated gravitationally induced particle creation in a cosmological framework, which is an essentially out-of-equilibrium process, this implies that all of Sakharov's conditions are satisfied in the simplest extension of General Relativity, without the need of CPT violation. Here, derivatives of the curvature can be disregarded, thus evading the potential problems associated with the Gravitational Baryogenesis (GB) model in a cosmological context. Thanks to the particle creation pressure and the trace anomaly, the curvature scalar is nonzero even in a radiation-dominated Universe. Moreover, the trace anomaly or the energy density of a massive scalar field can amplify the baryon asymmetry at very high temperatures, even when the particle creation rate is very slow. As a result, a baryon asymmetry compatible with observations and a huge CP violation can be generated in the early Universe.

gr-qc↗

arXiv2018

Charm rescattering contribution in rare $B^+_c \to K^+ K^- π^+$ decay

Following the experimental results from LHCb on the rare decay $B^+_c \to K^-K^+π^+$, we investigate the possibility where this process is dominated by a double charm rescattering. The $B_c$ decay to double charm channels have a weak topology that is favoured in comparison with the direct production of $K^-K^+π^+$ in the final state, suppressed by quark annihilation. The decay amplitude for $B^+_c \to K^-K^+π^+$ with $B_c$ decaying first to double charm channels is described by a charm penguin diagram, represented by charm hadronic triangle loops, which reach the final state of interest after $D\bar{D}\to K\bar{K}$ or $ D^+ D^-_s \to π^+ K^-$ transitions. We show that these processes give rise to non-resonant amplitudes with a clear signature in the Dalitz plot. In a near future, the new data from LHCb run II will be able to confirme if the main hypotheses of this work is correct and the dominant mechanism to produce $K^+K^+π^-$ from the decay of $B^+_c$ is through charm rescattering.

hep-ph↗

arXiv2017

Experimental overview of spectroscopy from heavy hadron decays

We present and discuss some experimental approaches involving spectroscopy from heavy meson decays going to light mesons. In particular we emphasis the scalar resonance $f_0(980)$, which have different well determined parameter of mass and width obtained from $J/ψ$ and D decays. We will also show how the CP violation observed in charmless three body decay can be used as tool to understand hadron hadron interaction at low mass region

hep-ex↗

arXiv2017

Charm Penguin in $B^\pm \to K^\pm K^+ K^-$: partonic and hadronic loops

Charm penguin diagrams are known to be the main contribution to charmless B decay process with strangeness variation equal to minus one, which is the case of $B^\pm \to K^\pm K^+ K^-$ decay. The large phase space available in this and other B three-body decays allows non trivial final state interactions with all sort of rescattering processes and also access high momentum transfers in the central region of the Dalitz plane. In this work we investigate the charm Penguin contribution to $B^\pm \to K^\pm K^+ K^-$, described by a hadronic triangle loop in nonperturbative regions of the phase space, and by a partonic loop at the quasi perturbative region. These nonresonant amplitudes should have a particular structure in the Dalitz plane and their contributions to the final decay amplitude can be confirmed by a data amplitude analysis in this channel. In particular, the hadronic amplitude has a changing sign in the phase at $D\bar{D}$ threshold which can result in a change of sign for the CP asymmetry.

hep-ph↗

arXiv2015

Phase motion in the $Z^-(4430)$ amplitude in $B^0\toψ^\primeπ^-K^+$ decay

In view of the proliferation in the number of new charmonium states, it is really important to have a experimental way to prove that an observed bump is, indeed, a real resonance. To do that, in this paper we present an alternative method to demonstrate the resonant behavior of a state. With this method, the phase variation of a generic complex amplitude can be directly revealed through interference in the Dalitz-plot region where it crosses a well established resonant state, used as a probe. We have tested the method for the $Z^-(4430)$ state by generating Monte Carlo samples for the $B^0\to ψ^\prime π^-K^+$ decay channel. We have shown that the proposed method gives a clear oscillation behavior, related to the phase variation associated to a real resonant state, in the case where the $Z^-(4430)$ is considered as a regular resonance with a strong phase variation. We have also discussed the possibility of using the proposed method complementary to the Argand diagram to determine the internal structure of the $Z^-(4430)$ state.

hep-ph↗

arXiv2014

Charmless B decays in modes with similar tree and penguin contributions

Charmless $B$ decays are dominated by contributions from the short distance amplitudes from tree level and penguin loop-level amplitudes. The Tree contribution presents a weak phase $γ$. The relationship between these two amplitudes can generated a CP asymmetry depending from the relative amount among them in a particular decay. In multi-body charmless $B$ decays, these relative contribution can change along the phase space, given a non isotropic distribution of CP asymmetries in the Dalitz plot. Two recent LHCb analyses involving charmless multi-body B decays are discussed: the obsevation of CP asymmetries in the phase space of the three-body decays $B^\pm \to π^\pm π^+ π^-$ and $B^\pm \to π^\pm K^+ K^-$; and the angular analysis of the $B^0 \to ϕK^*(892)^0$ decay.

hep-ex↗

arXiv2011

Heavy meson three body decay: Three decades of Dalitz plot amplitude analysis

Three body heavy meson decays allows one to extract important quantities for flavour physic, however the phenomenological analysis has some open problems to be solved in order to make possible to extract physical parameters with precision. After many years and some experience accumulated, we have learned new features and we expect to learn much more from data coming mainly from B three body decays. In this paper we address these aspects and we present a proposal to modify the Dalitz fit amplitude method in order to allow further studies.

hep-ph↗

arXiv2007

Extracting CKM $γ$ phase from $B^{\pm} \to K^{\pm} π^+ π^-$ and $B^0$, $\bar B^0 \to K_s π^+ π^-$

We discuss some aspects of the search for CP asymmetry in the three body B decays, revealed through the interference among neighbor resonances in the Dalitz plot. We propose a competitive method to extract the CKM $γ$ angle combining Dalitz plot amplitude analysis of $B^{\pm} \to K^{\pm} π^+ π^-$ and untagged $B^0$, $\bar B^0 \to K_s π^+ π^-$. The method also obtains the ratio and phase difference between the {\it tree} and {\it penguin} contributions from $B^0$ and $\bar B^0 \to K^{*\pm} π^{\mp} $ decays and the CP asymmetry between $B^0$ and $\bar{B^0}$. From Monte Carlo studies of 100K events for the neutral mesons, we show the possibility of measuring $γ$.

hep-ph↗

arXiv2007

CKM $γ$ phase from $B \to K ππ$

We discuss a method to extract the CKM $γ$ angle combining Dalitz plot analysis of $B^{\pm} \to K^{\pm} π^+ π^-$ and untagged $B^0$, $\bar B^0 \to K_s π^+ π^-$. The method also allows obtaining the ratio and phase difference between the {\it tree} and {\it penguin} contributions from $B^0$ and $\bar B^0 \to K^{*\pm} π^{\mp} $ decays and direct CP asymmetry between $B^0$ and $\bar{B^0}$. From Monte Carlo studies of 100K events for the neutral mesons, we show the possibility of measuring $γ$ with a precision of $\sim 5^o$.

hep-ph↗

arXiv2005

Phase Motion in the Scalar Low-Mass pi+pi- Amplitude in D+ -> pi-pi+pi+ Decay

Applying the Amplitude Difference method to Fermilab experiment E791 D+ -> pi-pi+pi+ data, we measure the low mass pi+pi- phase motion. Our results suggest a significant phase variation, compatible with the existence of an isoscalar sigma(500) meson, as previously reported using an isobar model fit to the full Dalitz-plot density.

hep-ex↗

arXiv2003

The structure of $f_0(980)$ from charmed mesons decays

We use the QCD sum rules to evaluate the form factors associated with the semileptonic decays of $D_s$ and $D$ mesons into $f_0(980)$. We consider the $f_0(980)$ meson as a quark-antiquark state with a mixture of strange and light components. The decay rates are evaluated in terms of the mixing angle. Using the same form factors to evaluate nonleptonic decays in the framework of the factorization approximation we conclude that the importance of the light quarks in $f_0(980)$ is not negligible.

hep-ph↗

arXiv2003

Phase Motion of the Scalar $ππ$ Amplitudes in $D^+$, $D^+_s \to π^-π^+π^+$ Decays

We make a direct and model-independent measurement of the low $π^+π^-$ mass phase motion in the $D^+ \to π^-π^+π^+$ decay. Our preliminary results show a strong phase variation, compatible with the isoscalar $σ(500)$ meson. This result confirms our previous result where we found evidence for the existence of this scalar particle using full Dalitz-plot analysis. We apply the Amplitude Difference (AD) method to the same Fermilab E791 data sample used in the preceding analysis. We also give an example of how we extract the phase motion of the scalar amplitude, looking at the $f_0(980)$ in $D^+_s \to π^-π^+π^+$ decay.

hep-ex↗

arXiv2003

$D_s$ decays into $ϕ$ and $f_0(980)$ mesons

We consider the nonleptonic and semileptonic decays of $D_s$-mesons into $ϕ$ and $f_0(980)$ mesons. QCD sum rules are used to calculate the form factors associated with these decays, and the correspondig decay rates. On the basis of data on $D_s^+\toπ^+π^+π^-$, which goes dominantly via the transition $D_s^+\to π^+f_0(980)$, we conclude that there is space for a sizeable light quark component on $f_0(980)$.

hep-ph↗

arXiv2002

Complex amplitude phase motion in Dalitz plot heavy meson three body decay

We propose a method to determine the phase motion of a complex amplitude in three body heavy meson decays. We show that the phase variation of a complex amplitude can be directly revealed through the interference observed in the Dalitz Plot region where it crosses with a well established resonant state. This method could be applied to the decays \d3pi and $D^+\to K^-π^+π^+$, to determine whether the low mass states $σ$ and $κ$, suggested by E791, have phase motions compatible with resonances.

hep-ph↗

arXiv2002

Light Scalar Mesons $σ(500)$, $f_0(980)$ and $κ$ in Charm Meson Decays

We present recent results on scalar light mesons based on Dalitz plot analyses of charm decays from Fermilab experiment E791. Scalar mesons are found to have large contributions to the decays studied, $D^+\to K^-π^+π^+$ and $D^+, D_s^+\toπ^-π^+π^+$. From the first decay, we find good evidence for the existence of the light and broad $κ$ meson and we measure its mass and width. We find strong evidence for the $σ(500)$ meson from $D^+\toπ^-π^+π^+$ decay and measure its mass and width. We also present the results obtained for the $f_0(980)$ parameters through the $D^+_s \toπ^-π^+π^+$ decay. These results demonstrate the importance of charm decays as a new environment for the study of light meson physics.

hep-ex↗