Measurements of the CKM Angle phi3/gamma Page: 1 of 11
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Measurements of the CKM angle #31/'
V. Tisserand, for the B4BAR and Belle collaborations.
Laboratoire de Physique des Particules (LAPP), IN2P3/CNRS et Universit6 de Savoie,
F-74941 Annecy-Le-Vieux, France
We present a review on the measurements of the CKM angle y (#3)1 as performed by the BABAR and Belle
experiments at the asymmetric-energy e+e- B factories colliders PEP-II and KEKB. These measurements
are using either charged or neutral B decays. For charged B decays the modes D0K--, *0K-, and b0K*-
are employed, where D0 indicates either a DO or a To meson. Direct CP violation is exploited. It is caused
by interferences between V1u and Vcb accessible transitions that generate asymmetries in the final states. For
these decays various methods exist to enhance the sensitivity to the V1u transition, carrying the weak phase y.
For neutral B decays, the modes D(*)-7r and D-p are used. In addition to the V1u and Vcb interferences,
these modes are sensitive to the BO-BO mixing, so that time dependent analyses are performed to extract
sin(2+ +y). An alternative method would use the lower branching ratios decay modes D(*)0K(*)0 where much
larger asymmetries are expected.
The various available methods are mostly "theoretically clean" and always free of penguins diagrams. In some
cases a high sensitivity to y is expected and large asymmetries may be seen. But these measurements are always
experimentally difficult as one has to face with either low branching ratios, or small asymmetries, or additional
technical/theoretical difficulties due to Dalitz/SU(3) and re-scattering models needed to treat/estimate nuisance
parameters such as unknown strong phases and the relative magnitude of the amplitude of the interfering "Vu6"
transitions. Thus at the present time only a relatively limited precision on y can be extracted from these
measurements. The current world average is y = (78-26)O . For other methods and long term perspectives,
as discussed in details, the reader is invited to consult the proceedings of the recent CKM workshop that was
held in Nagoya (Japan) in December 2006 .
We present the results of the measurements
performed by the BABAR and Belle collabora-
tions, to determine the value of the Cabibbo-
Kobayashi-Maskawa (CKM) CP violating phase -y
(_ arg [-VdVd*/VcdVK; ]).
These measurements are based on the studies done
with the charged B decays D0K-, D*0K-, and
D0K*-, where D0 indicates either a D or a D me-
son. They are based on the interference of the ampli-
tudes proportional to the Vbc and Vum CKM-matrix el-
ements that generate asymmetries through direct CP
violation effects associated to the electroweak (EW)
phase -y carried by the Vui amplitude. These mea-
surements are at the present time the most constrain-
ing ones, but neutral B decays such as D(*) r+
and D p+ are also used to extract constraints on
sin(2!3+y), as BO-B0 mixing is present in addition to
the above described direct CP violation phenomenon.
The sensitivity to the Vub amplitude is relatively small
for these decays, so it has been proposed to use the
rare decays D(*)0k(*)0 where larger CP asymmetries
At the time of this conference the two asymmetric-
energy e+c- colliders PEP-II at SLAC and KEKB at
'The BABAR and Belle collaborations use different conventions
to label the three CKM angles, where /3 =1, a #2, and
y = 03. In this report we use the BABAF convention: a, /3, and
KEK have produced a huge quantity of data at the
T(4S) resonance. BABAR  and Belle  detectors
have integrated over 1100 fb-1 of data (respectively
about 420 fb-i1 and 710 fb--1). This corresponds to a
sample of more than one billion BB pairs collected.
It can be noticed that the measurements presented
here are all statistically limited and most of them use
only a fraction of the currently available dataset. It is
therefore crucial that they will be updated soon.
2. Measuring y with charged B decays
Methods are exploited [5 7], where the 0 decays
either to a CP eigenstate (GLW method), or to a Dou-
bly Cabibbo-Suppressed flavor Decay (DCSD, "wrong
sign" decay, ADS method), or to the K7r-7r+ final
state, for which a Dalitz analysis has to be performed
(GGSZ method). To extract -y, those three methods
are all based on the fact that a B- can decay into
a color-allowed DK-- (color-suppressed ID K-) fi-
nal state via b -> cus (b -> ucs) transitions. The
amplitude A("Vcb") of the b -> cus transition is pro-
portional to A3 and the amplitude A("Vb") of the
b -> ucs transition to A3 42 + p2&001-) (where A is
the related to the Cabibbo angle). The second ampli-
tude therefore carries both the EW -y CP phase and
the relative strong phase of those two transitions. As
the total amplitude for the DK-- decay is the sum of
the two amplitudes A("Vcb") and A("Vb"), the two
amplitudes interfere when the D0 and D decay into
the same final state. This interference leads to dif-
Contributed to 5th Flavor Physics And CP Violation Conference (FPCP 2007), 12-16 May 2007, Bled, Slovenia
Work supported in part by US Department of Energy contract DE-AC02-76SF00515
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Tisserand, Vincent. Measurements of the CKM Angle phi3/gamma, article, June 27, 2007; [Menlo Park, California]. (https://digital.library.unt.edu/ark:/67531/metadc887409/m1/1/: accessed April 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.