Measurement of Direct CP Violating Asymmetries in Charmless Decays of Strange
Bottom Mesons and Bottom Baryons with 9.3 fb-1.
Primary authors: M.J. Morello, G. Punzi, F. Ruffini
This webpage collects the links to the CDF public note and to the
relevant supporting plots for the measurement of the measurements
of ACP (B0(s)->hh') and ACP(Λ0b->ph)
These preliminary results were approved on June 28th, 2012 by the CDF collaboration.
Non invariance of the fundamental interactions under the combined
symmetry transformation of charge conjugation and parity inversion (CP violation)
is an established experimental fact. The vast majority of experimental data are well described by the standard model (SM),
and have supported the success of the Cabibbo-Kobayashi-Maskawa
(CKM) theory of quark-flavor dynamics.
However, additional sources of CP violation are required to explain the matter-antimatter asymmetry of the Universe in standard big-bang cosmology. This would have profound consequences on our understanding of fundamental interactions.
Violation of CP is direct if the partial decay-width of a
particle into a final state differs from the width of the corresponding
antiparticle into the CP-conjugate final state.
In recent times, the pattern of direct CP violation in
charmless mesonic decays of B mesons has shown some
unanticipated discrepancies from expectations.
Under standard assumptions of isospin symmetry and smallness of contributions
from higher-order processes,
similar CP asymmetries are predicted
for B0→K+ π- and
B+→K+ π0 decays ,
However, experimental data show a significant discrepancy ,
which has prompted intense experimental and theoretical
activity. Several simple extensions of the standard model
could accommodate the discrepancy, but
uncertainty on the contribution of higher-order SM amplitudes
has prevented a firm conclusion.
Recently, it has been suggested a way  to accommodate this discrepancy within the SM, taking into account only constraints imposed by the Pauli principle.
Nevertheless, high accuracy measurements of the violation of CP
symmetry in charmless modes remains, therefore, a very interesting
subject of study and may provide useful information to our
comprehension of this discrepancy.
Rich samples of bottom-flavored hadrons of all types from the Tevatron offer the opportunity to explore
new territory in the field of Bs mesons and b-flavored baryons.
Additional information coming from different decays
yields further constraints on the possible
explanations of previous findings, and may possibly reveal new
deviations from expectations.
Specifically, measurements of direct CP violation in B0s→π+ K-
decays have been proposed as a nearly model-independent test for the
presence of non-SM physics .
The relationships between charged-current quark
couplings in the SM predict a well-defined hierarchy between direct
CP violation in B0→K+ π-
and B0s→π+ K-
decays, yielding a significant asymmetry for the latter, of about 30%. This large effect allows easier experimental
investigation and any discrepancy may indicate contributions from non-SM amplitudes.
Supplementary information could come from CP\ violation
in bottom baryons.
Interest in charmless b-baryon decays is prompted by branching fractions recently
observed being larger than expected .
Asymmetries up to about 10% are predicted for Λ0b->p π and Λ0b->pK decays
in the SM  and are accessible with current CDF event samples.
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Data and analysis
The data have been collected by the hadronic B trigger designed to select events containing track pairs exiting from a common
displaced vertex and correspond to about 9.3 fb-1 of integrated luminosity. This is an improvement of the measurement performed on
6 fb-1 (public web page
published on Phys. Rev. Lett. 108, 211803 (2012)
A complete description of the analysis is available here: CDF Public note 10726.
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These results can be compared with the B-Factories and LHCb measurements
The measurement of CP violation in the B mesons system is compatible
and of comparable accuracy with current results from B-Factories and LHCb.
We report an updated measurement of ACP in Bs->Kpi decays, with a
significance of about 3 sigma. This result confirms the LHCb evidence
with the same level of resolution.
The measurement of CP violation in the Bs mesons system is in
agreement at 2 sigma level with the prediction within the SM .
The observed asymmetry in the Λ0b->ph decays are consistent
with zero. However the limited experimental precision does not allow
a conclusive discrimination between SM prediction (~8%), much suppressed
values expected in supersymmetric scenarios (~0.3%), or prevision from
pQCD approach , that are 31% for
ACP(Λ0b->ppi) and 5%
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- Table: selection pdf
- Table: ACP results pdf
- Table: ACP results with raw yields pdf eps
- Table: systematic uncertainties pdf
- Qualitative Mass only fit eps
- Fit projection onto invariant pipi-mass eps log
- Fit projection onto invariant pipi-mass squared eps log
- Fit projection onto beta eps log
- Fit projection onto p(tot) eps log
- Fit projection onto k+ eps log
- Fit projection onto k- eps log
- Fit projection onto k+ + k- eps log
- Fit projection onto k+ - k- eps log
- Fit projection onto invariant pipi-mass eps
- Fit projection onto invariant pipi-mass square eps
- Fit projection onto beta eps
- Fit projection onto p_tot eps
- Fit projection onto k+ eps
- Fit projection onto k- eps
- Fit projection onto k+ + k- eps
- Fit projection onto k+ - k- eps
- Fit projection onto invariant pipi-mass squared versus (k+ + k-) eps
- Fit projection onto invariant pipi-mass squared versus (k+ - k-) eps
- Mass template (correct mass assignment) for B0->pipi eps log
- Mass template (correct mass assignment) for B0->Kpi eps log
- Mass template (correct mass assignment) for B0->KK eps log
- Mass template (correct mass assignment) for B0s->pipi eps log
- Mass template (correct mass assignment) for B0s->Kpi eps log
- Mass template (correct mass assignment) for B0s->KK eps log
- Mass template (correct mass assignment) for Lb->ppi eps log
- Mass template (correct mass assignment) for Lb->pK eps log
- Universal Curves for positive particles eps
- Universal Curves for negative particles eps
- dE/dx residual in pion hypothesis for positive pions and kaons eps
- dE/dx residual in pion hypothesis for negative pions and kaons
- Invariant pπ mass distribution for antiΛ0->pπ: fit overlaid eps
- Fit projection of the detector-induced charge asymmetry as a function of the invariant-pπ mass eps
- Invariant pπ mass distribution for Λ0->pπ: fit overlaid eps
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