Antonio Pich - Academia.edu (original) (raw)

Papers by Antonio Pich

Journal of High Energy Physics

Motivated by the persistent anomalies reported in the b → cτν data, we perform a general model-in... more Motivated by the persistent anomalies reported in the b → cτν data, we perform a general model-independent analysis of these transitions, in the presence of light right-handed neutrinos. We adopt an effective field theory approach and write a low-energy effective Hamiltonian, including all possible dimension-six operators. The corresponding Wilson coefficients are determined through a numerical fit to all available experimental data. In order to work with a manageable set of free parameters, we define eleven wellmotivated scenarios, characterized by the different types of new physics that could mediate these transitions, and analyse which options seem to be preferred by the current measurements. The data exhibit a clear preference for new-physics contributions, and good fits to the data are obtained in several cases. However, the current measurement of the longitudinal D * polarization in B → D * τν cannot be easily accommodated within its experimental 1σ range. A general analysis of the three-body B → Dτν and four-body B → D * (→ Dπ)τν angular distributions is also presented. The accessible angular observables are studied in order to assess their sensitivity to the different new physics scenarios. Experimental information on these distributions would help to disentangle the dynamical origin of the current anomalies.

Journal of High Energy Physics

We present the results of a global fit to the Aligned Two-Higgs Doublet Model, assuming that ther... more We present the results of a global fit to the Aligned Two-Higgs Doublet Model, assuming that there are no new sources of CP violation beyond the quark mixing matrix. We use the most constraining flavour observables, electroweak precision measurements and the available data on Higgs signal strengths and collider searches for heavy scalars, together with the theoretical requirements of perturbativity and positivity of the scalar potential. The combination of all these constraints restricts the values of the scalar masses, the couplings of the scalar potential and the flavour-alignment parameters. The numerical fits have been performed using the open-source HEPfit package.

Physical Review D

We analyze the constraints on coloured scalar bosons imposed by the current LHC data at √ s = 13 ... more We analyze the constraints on coloured scalar bosons imposed by the current LHC data at √ s = 13 TeV. Specifically, we consider an additional electroweak doublet of colouroctet scalars, satisfying the principle of minimal flavour violation in order to fulfill the stringent experimental limits on flavour-changing neutral currents. We demonstrate that coloured scalars with masses below 800 GeV are already excluded, provided they are not fermiophobic.

Journal of High Energy Physics

We present a comprehensive analysis of low-energy signals of hypothetical scalar leptoquark inter... more We present a comprehensive analysis of low-energy signals of hypothetical scalar leptoquark interactions in lepton and kaon transitions. We derive the most general effective four-fermion Lagrangian induced by tree-level scalar leptoquark exchange and identify the Wilson coefficients predicted by the five possible types of scalar leptoquarks. The current constraints on the leptoquark Yukawa couplings arising from lepton and kaon processes are worked out, including also loop-induced transitions with only leptons (or quarks) as external states. In the presence of scalar leptoquark interactions, we also derive the differential distributions for flavour-changing neutral-current transitions in semileptonic kaon modes, including all known effects within the Standard Model. Their interference with the new physics contributions could play a significant role in future improvements of those constraints that are currently hampered by poorly-determined non-perturbative parameters.

SciPost Physics Proceedings

We review the current status of the determination of the strong coupling from tau decay. Using th... more We review the current status of the determination of the strong coupling from tau decay. Using the most recent release of the ALEPH data, a very comprehensive phenomenological analysis has been performed, exploring all strategies previously considered in the literature and several complementary approaches. Once their actual uncertainties are properly assessed, the results from all adopted methodologies are in excellent agreement, leading to a very robust and reliable value of the strong coupling, \alpha_s^{(n_f=3)}(m_\tau^2) = 0.328\pm 0.013αs(nf=3)(mτ2)=0.328±0.013, which implies \alpha_s^{(n_f=5)}(M_Z^2) = 0.1197\pm 0.0015αs(nf=5)(MZ2)=0.1197±0.0015.

Nuclear and Particle Physics Proceedings

A brief overview of the main highlights discussed at ICHEP 2014 is presented. The experimental da... more A brief overview of the main highlights discussed at ICHEP 2014 is presented. The experimental data confirm that the scalar boson discovered at the LHC couples to other particles as predicted in the Standard Model. This constitutes a great success of the present theoretical paradigm, which has been confirmed as the correct description at the electroweak scale. At the same time, the negative searches for signals of new phenomena tightly constrain many newphysics scenarios, challenging previous theoretical wisdom and opening new perspectives in fundamental physics. Fresh ideas are needed to face the many pending questions unanswered within the Standard Model framework.

Nucl Phys B Proc Suppl, 1989

The progress done in the QCD-duality analysis of strangeness changing nonleptonic weak transition... more The progress done in the QCD-duality analysis of strangeness changing nonleptonic weak transitions is reviewed. The method combines the information provided by the effective chiral realization of QCD at long distances with its perturbative short-distance behaviour, via a duality approach. Special attention is given to the failure of the earlier leading-logarithm calculations in explaining the observed ~AII = ½ K + ~ amplitude.

Nucl Phys B Proc Suppl, 1999

The interplay between short-and long-distance contributions to the KL → µ + µ − decay amplitude i... more The interplay between short-and long-distance contributions to the KL → µ + µ − decay amplitude is analyzed. The long-distance piece is estimated using chiral perturbation theory techniques and large-NC considerations, leading to a consistent description of the π 0 → e + e − , η → µ + µ − and KL → µ + µ − branching ratios [1].

Metode Revista De Difusion De La Investigacion, 2013

Phys Lett B, 1992

The invariant-mass distribution of the hadronic nal state in decay can be used for testing fundam... more The invariant-mass distribution of the hadronic nal state in decay can be used for testing fundamental aspects of the strong interactions. Using standard QCD techniques, it is possible to compute certain weighted integrals of the hadronic spectrum. We w ork out some QCD predictions which will be useful for analysing the data. They provide a direct way to simultaneously measure s (m 2) and the parameters characterizing the non-perturbative dynamics, allowing for a better control of the theoretical errors in the determination of s (m 2).

Eprint Arxiv 1107 1123, Jul 6, 2011

The accurate determination of the strong coupling from tau decay data is briefly reviewed. The pr... more The accurate determination of the strong coupling from tau decay data is briefly reviewed. The present phenomenological status is summarized.

Eprint Arxiv Hep Ph 0505122, May 1, 2005

The recent update of the strange spectral function and the moments of the invariant mass distribu... more The recent update of the strange spectral function and the moments of the invariant mass distribution by the OPAL collaboration from hadronic τ decay data are employed to determine |Vus| as well as ms. Our result, |Vus| = 0.2208 ± 0.0034, is competitive to the standard extraction of |Vus| from Ke3 decays and to the new proposals to determine it. Furthermore, the error associated to our determination of |Vus| can be reduced in the future since it is dominated by the experimental uncertainty that will be eventually much improved by the Bfactories hadronic τ data. Another improvement that can be performed is the simultaneous fit of both |Vus| and ms to a set of moments of the hadronic τ decays invariant mass distribution, which will provide even a more accurate determination of both parameters.

Journal of High Energy Physics

Motivated by the persistent anomalies reported in the b → cτν data, we perform a general model-in... more Motivated by the persistent anomalies reported in the b → cτν data, we perform a general model-independent analysis of these transitions, in the presence of light right-handed neutrinos. We adopt an effective field theory approach and write a low-energy effective Hamiltonian, including all possible dimension-six operators. The corresponding Wilson coefficients are determined through a numerical fit to all available experimental data. In order to work with a manageable set of free parameters, we define eleven wellmotivated scenarios, characterized by the different types of new physics that could mediate these transitions, and analyse which options seem to be preferred by the current measurements. The data exhibit a clear preference for new-physics contributions, and good fits to the data are obtained in several cases. However, the current measurement of the longitudinal D * polarization in B → D * τν cannot be easily accommodated within its experimental 1σ range. A general analysis of the three-body B → Dτν and four-body B → D * (→ Dπ)τν angular distributions is also presented. The accessible angular observables are studied in order to assess their sensitivity to the different new physics scenarios. Experimental information on these distributions would help to disentangle the dynamical origin of the current anomalies.

Journal of High Energy Physics

We present the results of a global fit to the Aligned Two-Higgs Doublet Model, assuming that ther... more We present the results of a global fit to the Aligned Two-Higgs Doublet Model, assuming that there are no new sources of CP violation beyond the quark mixing matrix. We use the most constraining flavour observables, electroweak precision measurements and the available data on Higgs signal strengths and collider searches for heavy scalars, together with the theoretical requirements of perturbativity and positivity of the scalar potential. The combination of all these constraints restricts the values of the scalar masses, the couplings of the scalar potential and the flavour-alignment parameters. The numerical fits have been performed using the open-source HEPfit package.

Physical Review D

We analyze the constraints on coloured scalar bosons imposed by the current LHC data at √ s = 13 ... more We analyze the constraints on coloured scalar bosons imposed by the current LHC data at √ s = 13 TeV. Specifically, we consider an additional electroweak doublet of colouroctet scalars, satisfying the principle of minimal flavour violation in order to fulfill the stringent experimental limits on flavour-changing neutral currents. We demonstrate that coloured scalars with masses below 800 GeV are already excluded, provided they are not fermiophobic.

Journal of High Energy Physics

We present a comprehensive analysis of low-energy signals of hypothetical scalar leptoquark inter... more We present a comprehensive analysis of low-energy signals of hypothetical scalar leptoquark interactions in lepton and kaon transitions. We derive the most general effective four-fermion Lagrangian induced by tree-level scalar leptoquark exchange and identify the Wilson coefficients predicted by the five possible types of scalar leptoquarks. The current constraints on the leptoquark Yukawa couplings arising from lepton and kaon processes are worked out, including also loop-induced transitions with only leptons (or quarks) as external states. In the presence of scalar leptoquark interactions, we also derive the differential distributions for flavour-changing neutral-current transitions in semileptonic kaon modes, including all known effects within the Standard Model. Their interference with the new physics contributions could play a significant role in future improvements of those constraints that are currently hampered by poorly-determined non-perturbative parameters.

SciPost Physics Proceedings

We review the current status of the determination of the strong coupling from tau decay. Using th... more We review the current status of the determination of the strong coupling from tau decay. Using the most recent release of the ALEPH data, a very comprehensive phenomenological analysis has been performed, exploring all strategies previously considered in the literature and several complementary approaches. Once their actual uncertainties are properly assessed, the results from all adopted methodologies are in excellent agreement, leading to a very robust and reliable value of the strong coupling, \alpha_s^{(n_f=3)}(m_\tau^2) = 0.328\pm 0.013αs(nf=3)(mτ2)=0.328±0.013, which implies \alpha_s^{(n_f=5)}(M_Z^2) = 0.1197\pm 0.0015αs(nf=5)(MZ2)=0.1197±0.0015.

Nuclear and Particle Physics Proceedings

A brief overview of the main highlights discussed at ICHEP 2014 is presented. The experimental da... more A brief overview of the main highlights discussed at ICHEP 2014 is presented. The experimental data confirm that the scalar boson discovered at the LHC couples to other particles as predicted in the Standard Model. This constitutes a great success of the present theoretical paradigm, which has been confirmed as the correct description at the electroweak scale. At the same time, the negative searches for signals of new phenomena tightly constrain many newphysics scenarios, challenging previous theoretical wisdom and opening new perspectives in fundamental physics. Fresh ideas are needed to face the many pending questions unanswered within the Standard Model framework.

Nucl Phys B Proc Suppl, 1989

The progress done in the QCD-duality analysis of strangeness changing nonleptonic weak transition... more The progress done in the QCD-duality analysis of strangeness changing nonleptonic weak transitions is reviewed. The method combines the information provided by the effective chiral realization of QCD at long distances with its perturbative short-distance behaviour, via a duality approach. Special attention is given to the failure of the earlier leading-logarithm calculations in explaining the observed ~AII = ½ K + ~ amplitude.

Nucl Phys B Proc Suppl, 1999

The interplay between short-and long-distance contributions to the KL → µ + µ − decay amplitude i... more The interplay between short-and long-distance contributions to the KL → µ + µ − decay amplitude is analyzed. The long-distance piece is estimated using chiral perturbation theory techniques and large-NC considerations, leading to a consistent description of the π 0 → e + e − , η → µ + µ − and KL → µ + µ − branching ratios [1].

Metode Revista De Difusion De La Investigacion, 2013

Phys Lett B, 1992

The invariant-mass distribution of the hadronic nal state in decay can be used for testing fundam... more The invariant-mass distribution of the hadronic nal state in decay can be used for testing fundamental aspects of the strong interactions. Using standard QCD techniques, it is possible to compute certain weighted integrals of the hadronic spectrum. We w ork out some QCD predictions which will be useful for analysing the data. They provide a direct way to simultaneously measure s (m 2) and the parameters characterizing the non-perturbative dynamics, allowing for a better control of the theoretical errors in the determination of s (m 2).

Eprint Arxiv 1107 1123, Jul 6, 2011

The accurate determination of the strong coupling from tau decay data is briefly reviewed. The pr... more The accurate determination of the strong coupling from tau decay data is briefly reviewed. The present phenomenological status is summarized.

Eprint Arxiv Hep Ph 0505122, May 1, 2005

The recent update of the strange spectral function and the moments of the invariant mass distribu... more The recent update of the strange spectral function and the moments of the invariant mass distribution by the OPAL collaboration from hadronic τ decay data are employed to determine |Vus| as well as ms. Our result, |Vus| = 0.2208 ± 0.0034, is competitive to the standard extraction of |Vus| from Ke3 decays and to the new proposals to determine it. Furthermore, the error associated to our determination of |Vus| can be reduced in the future since it is dominated by the experimental uncertainty that will be eventually much improved by the Bfactories hadronic τ data. Another improvement that can be performed is the simultaneous fit of both |Vus| and ms to a set of moments of the hadronic τ decays invariant mass distribution, which will provide even a more accurate determination of both parameters.