Hot topics from Belle experiment
K. Ikado
We present the first evidence of the decay $B^{-}\rightarrow\tau^{-}\bar{\nu}_{\tau}$, using $414~fb^{-1}$ of data collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. Events are tagged by fully reconstructing one of the $B$ mesons in hadronic modes. We detect the signal with a significance of $4.0$ standard deviations including systematics, and measure the branching fraction to be ${\cal B}(B^{-}\rightarrow\tau^{-}\bar{\nu}_{\tau}) = (1.06^{+0.34}_{-0.28}(\mbox{stat})^{+0.22}_{-0.25}(\mbox{syst}))\times 10^{-4}$. We also report results based on $1.86\mbox{fb}^{-1}$ data collected by the Belle detector at the $\Upsilon(5S)$ resonance. Several exclusive $B_{s}$ decays $B_{s}\rightarrow D_{s}^{(*)+}\pi^{-}(\rho^{-})$ and $B_{s}\rightarrow J/\psi\phi(\eta)$ are studied. %Combining the $B_{s}\rightarrow D_{s}^{(*)+}\pi^{-}(\rho^{-})$ and %$B_{s}\rightarrow J/\psi\phi(\eta)$ decay modes, a signicant $B_{s}$ signal is observed. The $B_{s}$ meson production is found to proceed predominantly through the creation of $B_{s}^{*}\bar{B}_{s}^{*}$ pairs. Upper limits on $B_{s}\rightarrow K^+K^-$, $B_{s}\rightarrow\phi\gamma$, $B_{s}\rightarrow\gamma\gamma$ and $B_{s}\rightarrow D_{s}^{(*)+}D_{s}^{(*)-}$ decays are also reported.
fpcp2006_KojiIkado.tex
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Flavor Physics and CP Violation Conference, Vancouver, 2006
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%Title of paper
\title{Hot topics from Belle experiment}

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\author{K. Ikado}
\affiliation{Nagoya University, Nagoya, 464-8602, Japan}
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\begin{abstract}
We present the first evidence of the decay $B^{-}\rightarrow\tau^{-}\bar{\nu}_{\tau}$, 
using $414~\textrm{fb}^{-1}$ of data collected at the $\Upsilon(4S)$ resonance 
with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. 
Events are tagged by fully reconstructing one of the $B$ mesons in hadronic modes.
We detect the signal with a significance of $4.0$ standard deviations including systematics, 
and measure the branching fraction to be 
${\cal B}(B^{-}\rightarrow\tau^{-}\bar{\nu}_{\tau}) = 
 (1.06^{+0.34}_{-0.28}(\mbox{stat})^{+0.22}_{-0.25}(\mbox{syst}))\times 10^{-4}$.
We also report results based on $1.86\mbox{fb}^{-1}$ data 
collected by the Belle detector at the $\Upsilon(5S)$ resonance. 
Several exclusive $B_{s}$ decays $B_{s}\rightarrow D_{s}^{(*)+}\pi^{-}(\rho^{-})$ and 
$B_{s}\rightarrow J/\psi\phi(\eta)$ are studied.
%Combining the $B_{s}\rightarrow D_{s}^{(*)+}\pi^{-}(\rho^{-})$ and 
%$B_{s}\rightarrow J/\psi\phi(\eta)$ decay modes, a signicant $B_{s}$ signal is observed. 
The $B_{s}$ meson production is found to proceed predominantly through the creation of 
$B_{s}^{*}\bar{B}_{s}^{*}$ pairs. 
Upper limits on 
$B_{s}\rightarrow K^+K^-$, $B_{s}\rightarrow\phi\gamma$, $B_{s}\rightarrow\gamma\gamma$
and $B_{s}\rightarrow D_{s}^{(*)+}D_{s}^{(*)-}$ decays are also reported.

\end{abstract}

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\section{Introduction}
In the Standard Model (SM), the purely leptonic decay 
$B^{-}\rightarrow\tau^{-}\bar{\nu}_{\tau}$
proceeds via annihilation of $b$ and $\overline{u}$ quarks to a $W^-$ boson.
It provides a direct determination of the product of the $B$ meson decay 
constant $f_B$ and the magnitude of the
Cabibbo-Kobayashi-Maskawa (CKM) matrix element $|V_{ub}|$.
The branching fraction is given by
\begin{equation}
 \label{eq:BR_B_taunu}
{\cal B}(B^{-}\rightarrow\tau^{-}\bar{\nu}_{\tau}) 
= \frac{G_{F}^{2}m_{B}m_{\tau}^{2}}{8\pi}\left(1-\frac{m_{\tau}^{2}}
{m_{B}^{2}}\right)^{2}f_{B}^{2}|V_{ub}|^{2}\tau_{B},
\end{equation}
where $G_F$ is the Fermi coupling constant, 
$m_{B}$ and $m_{\tau}$ are the $B$ and $\tau$ masses, respectively, 
and $\tau_B$ is the $B^-$ lifetime~\cite{Eidelman:2004wy}.
%The expected branching fraction is  $(1.59\pm 0.40) \times 10^{-4}$
%using $|V_{ub}| = (4.39 \pm 0.33) \times 10^{-3}$, determined by inclusive
%charmless semileptonic $B$ decay data~\cite{HFAG}, $\tau_{B} = 1.643\pm 0.010$ ps ~\cite{HFAG},
%and $f_B = 0.216\pm 0.022$ GeV
%obtained from lattice QCD calculations~\cite{Gray:2005ad}.
Physics beyond the SM, such as supersymmetry or two-Higgs doublet models,
could modify ${\cal B}(B^{-}\rightarrow\tau^{-}\bar{\nu}_{\tau})$ through
the introduction of a charged Higgs boson~\cite{Hou:1992sy}.
Purely leptonic $B$ decays have not been observed in past experiments.
The most stringent upper limit on $B^{-}\rightarrow\tau^{-}\bar{\nu}_{\tau}$
comes from the BaBar experiment: 
${\cal B}(B^{-}\rightarrow\tau^{-}\bar{\nu}_{\tau}) < 2.6 \times 10^{-4}$
(90\% C.L.)~\cite{Aubert:2005}.

The possibility to study decays of $B_{s}$ at very high luminosity $e^+e^-$ colliders running
at the energy of the $\Upsilon(5S)$ resonance has been discussed in several theoretical
papers~\cite{Falk:2000ga,Atwood:2001js}. 
The first data at the $\Upsilon(5S)$ were taken many years ago at CESR~\cite{Lovelock:1985nb,Besson:1984bd,Lee-Franzini:1990gy},
but the collected data sample was not enough to observe a $B_{s}$ signal. 
In 2003, the CLEO experiment collected $0.42~\mbox{fb}^{-1}$ at the $\Upsilon(5S)$
and observed some evidence for $B_{s}$ meson production in both inclusive and exclusive modes. 
However, simple calculations assuming an approximate $SU(3)$ symmetry indicate that many
interesting $B_{s}$ measurements require a data sample of at least $20~\mbox{pb}^{-1}$, 
which can be collected by $B$ Factories in the future. 
To test the experimental feasibility of such measurements, a data sample of $1.86~\mbox{fb}^{-1}$
was recently taken with the Belle detector at the center-of-mass (CM) energy corresponding to the mass
of the $\Upsilon(5S)$ resonance.
This data sample is more than four times larger than the CLEO dataset
at the $\Upsilon(5S)$.

The Belle detector is a large-solid-angle
magnetic spectrometer consisting of a silicon vertex detector,
a $50$-layer central drift chamber (CDC), a system of aerogel threshold
$\check{\textrm{C}}$erenkov counters (ACC), time-of-flight scintillation
counters (TOF), and an electromagnetic calorimeter comprised of
CsI(Tl) crystals (ECL)
located inside a superconducting solenoid coil that provides a $1.5$ T
magnetic field. An iron flux-return located outside of the coil is
instrumented to identify $K_{L}^{0}$ and muons.
The detector is described in detail elsewhere~\cite{belle_detector:2003}.



\section{Evidence of the Purely Leptonic Decay \boldmath$B^{-}\rightarrow\tau^{-}\bar{\nu}_{\tau}$}

%===========================================================================
We use a $414~\textrm{fb}^{-1}$ data sample containing 
$447\times 10^{6}$ $B$ meson pairs collected with the Belle detector
at the KEKB asymmetric-energy $e^{+}e^{-}$ ($3.5$ on $8$ GeV) collider
operating at the $\Upsilon(4S)$ resonance ($\sqrt{s} = 10.58$ GeV). 

We use a detailed Monte Carlo (MC) simulation, which fully describes the
detector geometry and response based on GEANT~\cite{GEANT}, to determine
the signal selection efficiency and to study the background.
In order to reproduce effects of beam background, data taken with random
triggers for each run period are overlaid on simulated events. 
The $B^{-}\rightarrow\tau^{-}\bar{\nu}_{\tau}$ signal decay is generated 
by the EvtGen package~\cite{EvtGen}.
To model the background from $e^+e^- \to B\overline{B}$ and continuum 
$q\overline{q}~(q = u, d, s, c)$ production processes, large 
$B\overline{B}$ and $q\overline{q}$ MC samples 
corresponding to about twice the data sample
are used.
We also use MC samples for rare $B$ decay processes, such as charmless 
hadronic, radiative, electroweak decays and $b \to u$ semileptonic decays.

We fully reconstruct one of the $B$ mesons in 
the event, referred to hereafter as the tag side ($B_{\rm tag}$), 
and compare properties of the remaining particle(s), referred to as the 
signal side ($B_{\rm sig}$), to those expected for signal and background.
The method allows us to suppress strongly the combinatorial background 
from both $B\overline{B}$ and continuum events.
In order to avoid experimental bias, 
the signal region in data is not looked at until the event 
selection criteria are finalized.

The $B_{\rm tag}$ candidates are reconstructed in the following decay modes: 
$B^{+} \rightarrow \overline{D}{}^{(*)0} \pi^{+}$, 
$\overline{D}{}^{(*)0}\rho^{+}$, 
$\overline{D}{}^{(*)0}a_{1}^{+}$ 
and $\overline{D}{}^{(*)0}D_{s}^{(*)+}$.
The $\overline{D}$ mesons are reconstructed as 
$\overline{D}{}^{0}\rightarrow K^{+}\pi^{-}$, $K^{+}\pi^{-}\pi^{0}$,
$K^{+}\pi^{-}\pi^{+}\pi^{-}$, $K_{S}^{0}\pi^{0}$, $K_{S}^{0}\pi^{-}\pi^{+}$,
$K_{S}^{0}\pi^{-}\pi^{+}\pi^{0}$ and $K^{-}K^{+}$, and
the $D_{s}^{+}$ mesons are reconstructed as 
$D_{s}^{+}\rightarrow K_{S}^{0}K^{+}$ and $K^{+}K^{-}\pi^{+}$.
The $\overline{D}{}^{*0}$ and $D_{s}^{*+}$ mesons are reconstructed in
$\overline{D}{}^{*0} \to \overline{D}{}^0 \pi^0, \overline{D}{}^0 \gamma$,
and $D_{s}^{*+} \to D_{s}^{+} \gamma$ modes.  
The selection of $B_{\rm tag}$ candidates is based on the 
beam-constrained mass $M_{\rm bc}\equiv\sqrt{E_{\rm beam}^{2} - p_{B}^{2}}$
and the energy difference $\Delta E\equiv E_{B} - E_{\rm beam}$.
Here, $E_{B}$ and $p_{B}$ are the reconstructed energy and momentum
of the $B_{\rm tag}$ candidate in the $e^+e^-$ center-of-mass system,
and $E_{\rm beam}$ is the beam energy in the CM frame.
The selection criteria for $B_{\rm tag}$ are defined as
$M_{\rm bc}>5.27~\mbox{GeV}/c^{2}$ and $-80~\mbox{MeV} <\Delta E< 60~\mbox{MeV}$.
If an event has multiple $B_{\rm tag}$ candidates, we choose the one having
the smallest $\chi^{2}$ based on deviations from the nominal values of 
$\Delta E$, the $D$ candidate mass, and the $D^{*} - D$ mass difference if
applicable.
%By fitting the $M_{\rm bc}$ distribution to the sum of an empirical 
%parametrization of the background shape~\cite{Albrecht:1986nr} plus a 
%signal shape~\cite{Bloom:1983pc}, we estimate the number of $B_{\rm tag}$'s 
%and their purity in the selected region to be $6.80 \times 10^{5}$ and 
%$0.55$, respectively. 

%===========================================================================
In the events where a $B_{\rm tag}$ is reconstructed, we search for decays
of $B_{\rm sig}$ into a $\tau$ and a neutrino. 
Candidate events are required to have one or three charged track(s) on the
signal side with the total charge being opposite to that of $B_{\rm tag}$.
The $\tau$ lepton is identified in the five decay modes,
$\mu^{-}\bar{\nu}_{\mu}\nu_{\tau}$,
$e^{-}\bar{\nu}_{e}\nu_{\tau}$, 
$\pi^{-}\nu_{\tau}$,
$\pi^{-}\pi^{0}\nu_{\tau}$ and 
$\pi^{-}\pi^{+}\pi^{-}\nu_{\tau}$,
which taken together correspond to $81\%$ of all $\tau$ decays~\cite{Eidelman:2004wy}.
The muon, electron and charged pion candidates are selected based on
information from particle identification devices.
The leptons are selected with requirements that have efficiencies greater than 90\% 
for both muons and electrons in the momentum region above 1.2 GeV/$c$, and 
misidentification rates of less than 0.2\%(1.5\%) for electrons (muons) in 
the same momentum region. 
Kaon candidates are rejected for all charged tracks on the signal side.
The $\pi^0$ candidates are reconstructed by requiring the invariant mass of two
$\gamma$'s to satisfy $|M_{\gamma\gamma}-m_{\pi^0}| < 20~\mbox{MeV}/c^{2}$.
For all modes except $\tau^{-}\rightarrow\pi^{-}\pi^{0}\nu_{\tau}$, we reject events with 
$\pi^{0}$ mesons on the signal side.
%We place the following requirements on the track momentum in the CM frame,
%$p_{\ell} > 0.3~\textrm{GeV}/c$ for $\mu^{-}\bar{\nu}_{\mu}\nu_{\tau}$ and $e^{-}\bar{\nu}_{e}\nu_{\tau}$,
%$p_{\pi^{-}} > 1.0~\textrm{GeV}/c$ for $\pi^{-}\nu_{\tau}$,
%$p_{\pi^{-}\pi^{0}} > 1.2~\textrm{GeV}/c$ for $\pi^{-}\pi^{0}\nu_{\tau}$ and
%$p_{\pi^{-}\pi^{+}\pi^{-}} > 1.8~\textrm{GeV}/c$ for
%$\pi^{-}\pi^{+}\pi^{-}\nu_{\tau}$.
%We calculate the missing momentum of the event in the CM frame ($p_{\rm miss}$)
%from $p_B$ and the momenta of charged tracks and $\pi^0$'s on the signal side.
%We require
%$p_{\rm miss} > 0.2~\textrm{GeV}/c$ for $\mu^{-}\bar{\nu}_{\mu}\nu_{\tau}$ and 
%$e^{-}\bar{\nu}_{e}\nu_{\tau}$,
%$p_{\rm miss} > 1.0~\textrm{GeV}/c$ for $\pi^{-}\nu_{\tau}$,
%$p_{\rm miss} > 1.2~\textrm{GeV}/c$ for $\pi^{-}\pi^{0}\nu_{\tau}$ and
%$p_{\rm miss} > 1.8~\textrm{GeV}/c$ for $\pi^{-}\pi^{+}\pi^{-}\nu_{\tau}$.
%In order to suppress background where particles produced along the beam pipe
%escape detection, the cosine of the angle of the missing momentum 
%($\cos\theta_{\rm miss}^{*}$) is required to satisfy
%$-0.86 < \cos\theta_{\rm miss}^{*} < 0.95$
%in the CM frame.
%We further require the invariant mass of the visible decay products to satisfy
%$|M_{\pi\pi}-m_{\rho}| < 0.15~\mbox{GeV}/c^{2}$ and 
%$|M_{\pi\pi\pi}-m_{a_{1}^{-}}| < 0.3~\mbox{GeV}/c^{2}$.
All the selection criteria have been optimized to achieve the highest sensitivity in MC.


The most powerful variable for separating signal and background is the 
remaining energy in the ECL, denoted as $E_{\rm ECL}$, which is sum of
the energy of photons that are not associated with either the 
$B_{\rm tag}$ or the $\pi^{0}$ candidate from the 
$\tau^{-}\rightarrow \pi^{-}\pi^{0}\nu_{\tau}$ decay.
%For neutral clusters contributing to $E_{\rm ECL}$, we require a minimum 
%energy threshold of 50 MeV for the barrel and 100 (150) MeV for the forward (backward) endcap ECL.
%A higher threshold is used for the endcap ECL because the effect of beam
%background is more severe.
For signal events, $E_{\rm ECL}$ must be either zero or small value 
arising from beam background hits, therefore, signal events peak at 
low $E_{\rm ECL}$.
On the other hand, background events are distributed toward higher 
$E_{\rm ECL}$ due to the contribution from additional neutral clusters.



%===========================================================================
The $E_{\rm ECL}$ signal region is optimized for each $\tau$ decay mode based
on the MC simulation, and is defined by $E_{\rm ECL} < 0.2~\mbox{GeV}$ for the
$\mu^{-}\bar{\nu}_{\mu}\nu_{\tau}$, $e^{-}\bar{\nu}_{e}\nu_{\tau}$ and
$\pi^{-}\nu_{\tau}$ modes, and $E_{\rm ECL} < 0.3~\mbox{GeV}$ for
the $\pi^{-}\pi^{0}\nu_{\tau}$ and $\pi^{-}\pi^{+}\pi^{-}\nu_{\tau}$
modes. 
The $E_{\rm ECL}$ sideband region is defined by $0.4~\mbox{GeV} < E_{\rm ECL} < 1.2$ GeV 
for the $\mu^{-}\bar{\nu}_{\mu}\nu_{\tau}$, $e^{-}\bar{\nu}_{e}\nu_{\tau}$ and
$\pi^{-}\nu_{\tau}$ modes, and by $0.45~\mbox{GeV} < E_{\rm ECL} < 1.2$ GeV for
the $\pi^{-}\pi^{0}\nu_{\tau}$ and $\pi^{-}\pi^{+}\pi^{-}\nu_{\tau}$ modes.
Table~\ref{tab:signal_yields} shows the number of events found in the sideband 
region for data ($N_{\rm side}^{\rm obs}$) and for the background MC simulation 
($N_{\rm side}^{\rm MC}$) scaled to the equivalent integrated luminosity in data.
Their good agreement for each $\tau$ decay mode indicates the validity of the
background MC simulation.
Table~\ref{tab:signal_yields} also shows the number of the background MC events 
in the signal region ($N_{\rm sig}^{\rm MC}$).  
%According to the MC simulation, about 95\% (5\%) of the background events come 
%from $B\overline{B} (q\overline{q})$ processes. 
%The MC simulation predicts that the background in the signal region consists of
%$B^- \to D^{(*)0} \ell^- \bar{\nu}$ semileptonic decays (90\%) and rare $B$ decay
%processes (10\%). 
%About 30\% of the background have $K_L^0$ candidates in the KLM.


%==========================================================================
In order to validate the $E_{\rm ECL}$ simulation, we use a control sample
of events (double tagged events), where the $B_{\rm tag}$ is fully reconstructed 
as described above and $B_{\rm sig}$ is reconstructed in the decay chain, 
$B^{-} \rightarrow D^{*0}\ell^{-}\bar{\nu}$ ($D^{*0}\rightarrow D^{0}\pi^{0}$),
followed by $D^0 \to K^- \pi^+$ or $K^- \pi^- \pi^+ \pi^+$
where $\ell$ is a muon or electron.
The sources affecting the $E_{\rm ECL}$ distribution in the control sample 
are similar to those affecting the $E_{\rm ECL}$ distribution in the signal 
MC simulation.
Figure~\ref{fig:controlsample} shows the $E_{\rm ECL}$ distribution in the
control sample for data and the MC simulation scaled to 
equivalent integrated luminosity in data.
Their agreement demonstrates the validity of the $E_{\rm ECL}$ simulation 
in the signal MC.


% --------------------------------------------------
\begin{figure}
\begin{center}
 \includegraphics[width=80mm]{fig1.eps}
\caption{$E_{\rm ECL}$ distribution for the control sample of doubly tagged events, where one $B$ is fully
  reconstructed and the other $B$ is reconstructed as $B^{-} \rightarrow D^{*0}\ell^{-}\bar{\nu}$. 
  The dots with errors indicate the data. The solid histogram represents the distribution as
  deduced background from 
  $B\overline{B}$ MC ($B^+B^- + B^0\overline{B}{}^0$), and the dashed histogram shows the contribution 
  from $B^0\overline{B}{}^0$ events.}
    \label{fig:controlsample}
\end{center}   
\end{figure}


After finalizing the signal selection criteria, the signal region is examined.
Figure~\ref{ecl_opened} shows the obtained $E_{\rm ECL}$ distribution
when all $\tau$ decay modes are combined.
One can see a significant excess of events in the $E_{\rm ECL}$ signal region
below $E_{\rm ECL}< 0.25$ GeV.
Table~\ref{tab:signal_yields} shows the number of events observed in the 
signal region ($N_{\rm obs}$) for each $\tau$ decay mode.
For the events in the signal region, we verify that the distributions of the 
event selection variables other than $E_{\rm ECL}$, such as $M_{\rm bc}$ and
$p_{\rm miss}$, are consistent with the sum of the signal and background
distributions expected from MC.
%The excess is robust against a cut requiring no $K_L^0$ candidate.


% -------------------------------------------------
\begin{figure}
\begin{center}
 \includegraphics[width=80mm]{fig2.eps} 
\caption{$E_{\rm ECL}$ distributions in the data after
	all selection requirements except the one on $E_{\rm ECL}$ 
	have been applied. The data and background MC samples are represented by the points with error bars
	and the solid histogram, respectively. 
	%The dashed histogram indicates 
	%the $B^{-}\rightarrow\tau^{-}\overline{\nu}_{\tau}$ signal distribution from MC. 
	The solid curve shows the result of the fit with the sum of the signal shape (dashed) and background shape
	(dotted).
}
    \label{ecl_opened}
\end{center}   
\end{figure}




%==========================================================================
We deduce the final results by fitting the obtained $E_{\rm ECL}$ 
distributions to the sum of the expected signal and background shapes.
Probability density functions (PDFs) for the signal $f_s(E_{\rm ECL})$ and
for the background $f_b(E_{\rm ECL})$ are constructed for each $\tau$ decay
mode from the MC simulation.
The signal PDF is modeled as the sum of a Gaussian function, centered at
$E_{\rm ECL} = 0$, and an exponential function.
The background PDF, as determined from the MC simulation, is parametrized 
by a second-order polynomial.
The PDFs are combined into an extended likelihood function,
\begin{equation}
{\cal L} = \frac{e^{-(n_{s}+n_{b})}}{N!}\prod_{i=1}^{N}(n_{s}f_{s}(E_{i})+n_{b}f_{b}(E_{i})),
\end{equation}
where $E_{i}$ is the $E_{\rm ECL}$ in the $i$th event, $N$ is the total number 
of events in the data, and $n_{s}$ and $n_{b}$ are the signal yield and background 
yield to be determined by the fit.
To combine likelihood functions of the five decay modes, we multiply 
the likelihood functions to produce the combined likelihood 
(${\cal L}_{\rm com} = \prod_{j=1}^{5} {\cal L}_{j}$).
The results are listed in Table~\ref{tab:signal_yields}.
The number of signal events in the signal region deduced from the fit ($N_{\rm s}$) is $21.2^{+6.7}_{-5.7}$
when all $\tau$ decay modes are combined.
Table~\ref{tab:signal_yields} also gives the number of background events 
in the signal region deduced from the fit ($N_{\rm b}$), which is 
consistent with the expectation from the background MC simulation 
($N_{\rm sig}^{\rm MC}$). 

The branching fractions are calculated as
${\cal B} = N_{s}/(2\cdot\varepsilon\cdot N_{B^{+}B^{-}})$
where $N_{B^{+}B^{-}}$ is the number of $\Upsilon(4S)\rightarrow B^{+}B^{-}$ 
events, assumed to be half of the number of produced $B$  meson pairs. 
The efficiency is defined as 
$\varepsilon = \varepsilon^{\rm tag}\times\varepsilon^{\rm sel}$,
where $\varepsilon^{\rm tag}$ is the tag reconstruction efficiency for events with 
$B^{-}\rightarrow\tau^{-}\bar{\nu}_{\tau}$ decays on the signal side, determined by MC
to be $0.136\pm 0.001({\rm stat})\%$,  and $\varepsilon^{\rm sel}$ is the event selection 
efficiency listed in Table~\ref{tab:signal_yields}, as 
determined by the ratio of the number of events surviving all of the 
selection criteria including the $\tau$ decay branching fractions over the number of fully 
reconstructed $B^{\pm}$.
When all $\tau$ decay modes are combined
we obtain a branching fraction of $(1.06^{+0.34}_{-0.28}) \times 10^{-4}$.
The branching fraction for each $\tau$ decay mode is consistent within  
error as shown in Table~\ref{tab:signal_yields}.

\begin{table*}
  \renewcommand{\baselinestretch}{1.3}
    \begin{tabular}{|c|c|c|c|c|c|c|c|c|c|} \hline
&$N_{\rm side}^{\rm obs}$ &$N_{\rm side}^{\rm MC}$ &$N_{\rm sig}^{\rm MC}$ &$N_{\rm obs}$ &$N_{\rm s}$ &$N_{\rm b}$
&$\varepsilon^{\rm sel}(\%)$  &${\cal B}(10^{-4})$  &$\Sigma$\\\hline
$\mu^{-}\bar{\nu}_{\mu}\nu_{\tau}$ &$96$   &$94.2\pm 8.0$   &$9.4\pm 2.6$  &$13$ &$5.4^{+3.2}_{-2.2}$  &$9.1^{+0.2}_{-0.1}$ &$8.88\pm 0.05$   &$1.01^{+0.59}_{-0.41}$ &$2.0\sigma$\\\hline
$e^{-}\bar{\nu}_{e}\nu_{\tau}$     &$93$   &$89.6\pm 8.0$   &$8.6\pm 2.3$  &$12$ &$3.9^{+3.5}_{-2.5}$  &$9.2^{+0.2}_{-0.2}$ &$8.18\pm 0.05$   &$0.79^{+0.71}_{-0.49}$ &$1.3\sigma$\\\hline
$\pi^{-}\nu_{\tau}$                &$43$   &$41.3\pm 6.2$   &$4.7\pm 1.7$  &$9$  &$3.4^{+2.6}_{-1.6}$  &$4.0^{+0.2}_{-0.1}$ &$5.79\pm 0.04$   &$0.96^{+0.74}_{-0.46}$ &$1.9\sigma$\\\hline
$\pi^{-}\pi^{0}\nu_{\tau}$         &$21$   &$23.3\pm 4.7$   &$5.9\pm 1.9$  &$11$ &$6.2^{+3.9}_{-2.7}$  &$4.2^{+0.3}_{-0.3}$ &$8.32\pm 0.08$   &$1.23^{+0.77}_{-0.53}$ &$2.3\sigma$\\\hline
$\pi^{-}\pi^{+}\pi^{-}\nu_{\tau}$  &$21$   &$18.5\pm 4.1$   &$4.2\pm 1.6$  &$9$  &$3.1^{+3.1}_{-2.6}$  &$3.7^{+0.3}_{-0.2}$ &$1.75\pm 0.03$   &$2.99^{+3.01}_{-2.49}$ &$1.2\sigma$\\
\hline
Combined                           &$274$  &$266.9\pm 14.3$ &$32.8\pm 4.6$ &$54$ &$21.2^{+6.7}_{-5.7}$ &$30.2^{+0.5}_{-0.4}$ &$32.92\pm 0.12$  &$1.06^{+0.34}_{-0.28}$   &$4.0\sigma$\\

\hline
    \end{tabular}
    \caption{The number of observed events in data in the sideband region $(N_{\rm side}^{\rm obs})$,
      number of background MC events in the sideband region $(N_{\rm side}^{\rm MC})$ and the 
      signal region $(N_{\rm sig}^{\rm MC})$,
      number of observed events in data in the signal region $(N_{\rm obs})$, 
      number of signal $(N_{\rm s})$ and background $(N_{\rm b})$ in the signal region determined by the fit, 
      signal selection efficiencies $(\varepsilon^{\rm sel})$, 
      extracted branching fraction $({\cal B})$ for $B^{-}\rightarrow\tau^{-}\bar{\nu}_{\tau}$.
      The listed errors are statistical 
      only. The last column gives the significance of the signal including 
      the systematic uncertainty in the signal yield ($\Sigma$).}
   \label{tab:signal_yields}
\end{table*}


%==========================================================================
Systematic errors for the measured branching fraction are associated with 
the uncertainties in the  number of $B^{+}B^{-}$, signal yields and  
efficiencies.
%The systematic error due to the uncertainty in $N_{B^{+}B^{-}}$ is $1$\%.
%The uncertainty in the signal yields arises from uncertainties
%in the signal and background shape, and is determined to be 
%$^{+16.7}_{-20.8}$\%.
%%$^{+11.9}_{-9.5}$\%.
%Here the uncertainty due to the signal shape uncertainty is determined 
%by varying the signal PDF parameters by the amount of difference 
%of each parameter between data and MC for the control sample of double tagged events.
%As for the background shape uncertainty, we change the samples used to 
%determine the PDF parameters from MC to sideband data.
%We also change the functional form used for the background PDF to a thrid-order 
%polynomial to address possible deviation of the real background shape from the
%second-order one, which can be caused by a peaking component from the rare decay 
%backgrounds, as noticed at the lowest $E_{ECL}$ bin in Figure~\ref{ecl_opened}. 
%We then add in quadrature the variations for the signal and background
%shapes.
%We take a $10.5\%$ error as the systematic error associated with the tag reconstruction 
%efficiency from the difference of yields between data and MC for the control sample.
%This value includes the error in the branching fraction
%${\cal B}(B^{-}\rightarrow D^{*0}\ell^{-}\bar{\nu})$, which we estimate from 
%${\cal B}(B^{0}\rightarrow D^{*-}\ell^{+}\nu)$ in~\cite{Eidelman:2004wy}
%and isospin.
%The systematic error in the signal efficiencies depends on the $\tau$ decay
%mode, and arises from the uncertainty in tracking efficiency ($1-3\%$), 
%$\pi^{0}$ reconstruction efficiency ($3\%$), particle identification 
%efficiency ($2-6\%$), branching fractions of $\tau$ leptonic decays 
%($0.3-1.1\%$), and Monte Carlo statistics ($0.6-2\%$).
%These efficiency errors sum up to 5.6\% for the combined result after 
%taking into account the correlations between the five $\tau$ decay modes, 
%based on the method described in~\cite{Lyons:1988rp}.
The total fractional uncertainty of the combined measurement is 
$^{+20.5}_{-24.0}\%$, 
%$^{+16.9}_{-15.3}\%$, 
and we measure the branching fraction to be
$$
{\cal B}(B^{-}\rightarrow\tau^{-}\bar{\nu}_{\tau}) 
= (1.06^{+0.34}_{-0.28}(\mbox{stat})^{+0.22}_{-0.25}(\mbox{syst}))\times 10^{-4}.
%= (1.06^{+0.34}_{-0.28}(\mbox{stat})^{+0.18}_{-0.16}(\mbox{syst}))\times 10^{-4}.
$$
The significance is $4.0\sigma$ when all $\tau$ decay modes are combined, 
where the significance is defined as 
$\Sigma = \sqrt{-2\ln({\cal L}_{0}/{\cal L}_{\rm max})}$,
where ${\cal L}_{\rm max}$ and ${\cal L}_{0}$ denote the maximum likelihood 
value and likelihood value obtained assuming zero signal events, respectively.
Here the likelihood function from the fit is convolved with a Gaussian
systematic error function in order to include the systematic uncertainty
in the signal yield.

%In conclusion, we have found the first evidence of the purely leptonic decay
%$B^{-}\rightarrow\tau^{-}\bar{\nu}_{\tau}$ from a data sample of $447\times 10^{6}$
%$B\bar{B}$ pairs collected at the $\Upsilon(4S)$ resonance with the Belle 
%experiment. 
%We find $21.2^{+6.7}_{-5.7}$ signal events with a significance of $4.0$ 
%standard deviations.
%The measured branching fraction is
%%$(1.06^{+0.34}_{-0.28}(\mbox{stat})^{+0.18}_{-0.16}(\mbox{syst}))\times 10^{-4}$.
%$(1.06^{+0.34}_{-0.28}(\mbox{stat})^{+0.22}_{-0.25}(\mbox{syst}))\times 10^{-4}$.
%The result is consistent with the SM prediction within errors.
%Using the measured branching fraction and known values of $G_F$, $m_B$, 
%$m_{\tau}$~\cite{Eidelman:2004wy} and $\tau_B$~\cite{HFAG}, the product
%of the $B$ meson decay constant $f_B$ and the magnitude of the 
%Cabibbo-Kobayashi-Maskawa matrix element $|V_{ub}|$ 
%is determined to be 
%%$f_{B} \cdot |V_{ub}| = (7.73^{+1.24}_{-1.02}(\mbox{stat})^{+0.58}_{-0.51}(\mbox{syst}))
%%\times 10^{-4}$ GeV.
%$f_{B} \cdot |V_{ub}| = (7.73^{+1.24}_{-1.02}(\mbox{stat})^{+0.80}_{-0.91}(\mbox{syst}))
%\times 10^{-4}$ GeV.
%Using the value of $|V_{ub}|$ from~\cite{HFAG}, we obtain 
%%%$f_{B} = 0.176^{+0.028}_{-0.023}(\mbox{stat})^{+0.020}_{-0.019}(\mbox{syst})$ GeV,
%$f_{B} = 0.176^{+0.028}_{-0.023}(\mbox{stat})^{+0.023}_{-0.025}(\mbox{syst})$ GeV,
%the first direct determination of the $B$ meson decay constant.


\section{Results from the \boldmath$\Upsilon(5S)$ Engineering Run}

We use a data sample of $1.86~\textrm{fb}^{-1}$ taken at the $\Upsilon(5S)$ energy of
$\sim 10869$ MeV. The experimental conditions of data taking at $\Upsilon(5S)$ are identical
to that for $\Upsilon(4S)$ or continuum running. The data sample of $3.67~\textrm{fb}^{-1}$ taken in
the continuum at an energy of $60$ MeV below the $\Upsilon(4S)$ was also used in this analysis for
comparison.

The $B_{s}$ mesons are produced at the $\Upsilon(5S)$ through
the intermediate $B_{s}\bar{B}_{s}$, $B_{s}^{*}\bar{B}_{s}$, $B_{s}\bar{B}_{s}^{*}$ or
$B_{s}^{*}\bar{B}_{s}^{*}$ pair production channels, where $B_{s}^{*}$ decays to $B_{s}\gamma$.
These intermediate channels can be distinguished kinematically and
their production ratios can be obtained from the reconstruction of exclusive $B_{s}$ decays.
To improve the statistical significance of our exclusive $B_{s}$ signal, we combined the
six modes 
$B_{s}\rightarrow D_{s}^{+}\pi^-$, 
$B_{s}\rightarrow D_{s}^{*+}\pi^-$,
$B_{s}\rightarrow D_{s}^{+}\rho^-$, 
$B_{s}\rightarrow D_{s}^{*+}\rho^-$,
$B_{s}\rightarrow J/\psi\phi$ and 
$B_{s}\rightarrow J/\psi\eta$
,which have large reconstruction efficiencies and are described by
unsuppressed conventional tree diagrams.
%Charged tracks are required to have momentum $p > 100~textrm{MeV}/c$. Kaon and pion
%mass hypotheses are assigned using a likelihood ratio 
%${\cal L}_{K/\pi} = {\cal L}_{K}/({\cal L}_{K} + {\cal L}_{\pi})$, obtained
%by combining information from the CDC ($dE/dx$), ACC, and TOF systems.
%We require ${\cal L}_{K/\pi} > 0.6$ (${\cal L}_{K/\pi} < 0.6$) for kaon (pion) candidates. 
%The tighter kaon identication cut ${\cal L}_{K/\pi} > 0.8$ is applied only for the 
%$B_{s}\rightarrow K^{+}K^{-}$ decay,
%where the pion misidentication background is large.
%Standard procedures are used to identify leptons. Electrons are identied using
%a combination of specic ionization ($dE/dx$) from the CDC, the ACC response,
%and electromagnetic shower position, shape and energy from the ECL. Muons
%are identied by matching to KLM hits and penetration depth.
%ECL clusters with a photon-like shape and energy larger than $50$ MeV, that are
%not associated with charged tracks, are accepted as photon candidates.
%Candidate primary photons ($\gamma$), that used fo reconstruct the 
%$B_{s}\rightarrow\phi\gamma$ and $B_{s}\rightarrow\gamma\gamma$ decays,
%are required to have a proper bunch cross timing and to lie within the acceptance
%of the barrel ECL ($33^{\circ} < \theta_{\gamma} < 128^{\circ}$). 
%To reduce the background from high energy $\pi^{0}$'s, represented by the two daughter 
%photons merged in a single cluster in the calorimeter, the ratio of the energy 
%deposition in $3\times 3$ ECL cells compared to that
%in $5\times 5$ cells around the maximum energy ECL cell is required to exceed $95\%$.
%The main background sources of these high energy photons are 
%$\pi^{0}\rightarrow\gamma\gamma$ and $\eta\rightarrow\gamma\gamma$ decays. 
%To reduce these backgrounds, restrictions are imposed on the
%invariant mass of the candidate primary photon and any other photon ($\gamma^{'}$) in the
%event. The primary photon is rejected if 
%$120~\mbox{MeV}/c^{2} < M(\gamma\gamma^{'}) < 145~\mbox{MeV}/c^{2}$ and
%$E_{\gamma^{'}} > 30$ MeV or if 
%$510~\mbox{MeV}/c^{2} < M(\gamma\gamma^{'}) < 570~\mbox{MeV}/c^{2}$ and 
%$E_{\gamma^{'}} > 200$ MeV.
%$\pi^{0}$ candidates are formed from pairs of photons, each with energy greater than
%$150$ MeV, with an invariant mass within $\pm 15~\mbox{MeV}/c^{2}$ of the $pi^{0}$ mass.
%We reconstruct $\eta$ mesons only in the clean $\eta\rightarrow\gamma\gamma$mode, 
%requiring an invariant mass to be within the $|M(\gamma\gamma) - M(\eta)| < 20~\mbox{MeV}/c^{2}$
%range.
%$K_{S}^{0}$ candidates are formed from $\pi^{+}\pi^{-}$ pairs with an invariant mass within
%$10~\mbox{MeV}/c^{2}$ of the nominal $K_{S}^{0}$ mass.
%Invariant masses of $\bar{K}^{*0}\rightarrow K^{-}\pi^{+}$ candidates are required to be within
%$50~\mbox{MeV}/c^{2}$ of the nominal $K^{*0} mass$; those of $\phi\rightarrow K^{+}K^{-}$
%candidates, within $12~\mbox{MeV}/c^{2}$ of the  mass. 
%The mass window $100~mbox{MeV}/c^{2}$ is used to select $\rho^{+}$ candidates reconstructed 
%in $\rho^{+}\rightarrow\pi^{+}\pi^{0}$ mode. $D_{s}^{+}$ mesons are reconstructed
%in the $\phi\pi^{+}$, $\bar{K}^{*0}K^{+}$ and $K_{S}^{0}K^{+}$ decay channels.
%$D_{s}^{*+}$ candidates are reconstructed in $D_{s}^{*+}\rightarrow D_{s}^{+}\gamma$ mode.

Six conventional $B_{s}$ decays to $D_{s}^{+}\pi^{-}$, $D_{s}^{+}\rho^{-}$, 
$D_{s}^{*+}\pi^{-}$, $D_{s}^{*+}\rho^{-}$, $J/\psi\phi$ and $J/\psi\eta$
final states and four rare $B_{s}$ decays to $K^+K^-$, $\phi\gamma$, $\gamma\gamma$ and
$D_{s}^{(*)+}D_{s}^{(*)-}$ final states are reconstructed.
The signals can be observed using two variables:
the energy difference $\Delta E = E_{B_{s}}^{\rm CM} - E_{\rm beam}^{\rm CM}$
and beam-constrained mass $M_{\rm bc} = \sqrt{(E_{\rm beam}^{\rm CM})^{2}
- (p_{B_{s}}^{\rm CM})^2 }$; 
$E_{B_{s}}^{\rm CM}$ and $p_{B_{s}}^{\rm CM}$
are the energy and momentum of the $B_{s}$ candidate in the CM 
system and $E_{\rm beam}^{\rm CM}$ is the CM beam energy. 
The $B_{s}$ mesons can be produced at the $\Upsilon(5S)$ energy via the intermediate
$e^+e^-\rightarrow B_{s}^{(*)}\bar{B}_{s}^{(*)}$ channels, with 
$B_{s}^{*}\rightarrow B_{s}\gamma$.
The $B_{s}$ signal regions in $M_{\rm bc}$ and $\Delta E$ are separated for 
different intermediate channels. 

After all selections, the dominant background is from $e^+e^-\rightarrow q\bar{q}$
continuum events ($q = u,~d,~s,~\mbox{or}~c$). 
%Topologically $B_{s}$ events are expected to be spherical,
%whereas the continuum events are expected to be jet-like.
The distribution of data in $M_{\rm bc}$ and $\Delta E$ for the 
$B_{s}\rightarrow D_{s}^+\pi^-$ decay mode is shown in Figure~\ref{fig:mbc_deltae}a. 
Three $D_{s}^+$ decay modes, $\phi\pi^+$, $\bar{K}^{*0}K^+$ and $K_{S}^{0}K^+$, are used
to reconstruct $B_{s}$ candidates.
Nine events are observed within the $B_{s}$ signal ellipsoidal region corresponding to 
$B_{s}^{*}\bar{B}_{s}^{*}$ pair production channel. 
Only one event is observed in the $B_{s}$ signal region for 
$B_{s}^{*}\bar{B}_{s} + B_{s}\bar{B}_{s}^{*}$ channels, 
and no events are observed for $B_{s}\bar{B}_{s}$ channel. 
Background outside the signal regions is small and corresponds to $0.1$ event 
for any of three signal regions.
The inclusive studies at the $\Upsilon(5S)$ found that $92,000\pm 7,900\pm 23,500$
$B_{s}^{(*)}\bar{B}_{s}^{(*)}$ pairs are contained within that $1.86~\mbox{fb}^{-1}$~
$\Upsilon(5S)$ data sample. 
Using this value, we measure the branching fraction to be 
${\cal B}(B_{s}\rightarrow D_{s}^+\pi^-) = (0.65\pm  0.21\pm  0.19)\%$. 


The $M_{\rm bc}$ and $\Delta E$ scatter plots are also obtained for the 
$B_{s}\rightarrow D_{s}^{*+}\pi^-$ (Figure~\ref{fig:mbc_deltae}b)
and $B_{s}\rightarrow D_{s}^{(*)+}\rho^-$ (Figure~\ref{fig:mbc_deltae}c) decay modes. 
Again, three $D_{s}^+$ decay modes, $\phi\pi^+$, $\bar{K}^{*0}K^+$ and $K_{S}^{0}K^+$, are used
to reconstruct $B_{s}$ candidates.
The numbers of events within the $B_{s}$ signal region for the $B_{s}^{*}\bar{B}_{s}^{*}$
pair production channel are $4$ for $B_{s}\rightarrow D_{s}^{*+}\pi^-$ decay and 
$7$ for $B_{s}\rightarrow D_{s}^{(*)+}\rho^-$ decay. 

The scatter plot in $M_{\rm bc}$ and $\Delta E$ for the $B_{s}\rightarrow J/\psi\phi$
and $B_{s}\rightarrow J/\psi\eta$ decays is shown in Figure~\ref{fig:mbc_deltae}d. 
One of the observed $B_{s}\rightarrow J/\psi\phi$ candidates is reconstructed 
in the $J/\psi\rightarrow\mu^{+}\mu^{-}$ mode and one in the 
$J/\psi\rightarrow e^{+}e^{-}$ mode. 
These two candidates correspond roughly to a branching fraction of
$\sim 1\times 10^{-3}$, in agreement with expectations.


% --------------------------------------------------
\begin{figure}
\begin{center}
 \includegraphics[width=80mm]{fig3.eps}
\caption{The $M_{\rm bc}$ and $\Delta E$ scatter plot for $B_{s}\rightarrow D_{s}^+\pi^-$(a),
$B_{s}\rightarrow D_{s}^{*+}\pi^-$(b) and $B_{s}\rightarrow D_{s}^{(*)+}\rho^-$(c) decay modes are shown,
where $D_{s}^{+}$ meson is reconstructed in the $D_{s}^{+}\rightarrow\phi\pi^{+}$, $D_{s}^{+}\rightarrow \bar{K}^{*0} K^{+}$
and $D_{s}^{+}\rightarrow K_{S}^{0} K^{+}$ decay modes. Also $M_{\rm bc}$ and $\Delta E$ scatter plot (d) is shown for
the $B_{s}\rightarrow J/\psi\phi$ and $B_{s}\rightarrow J/\psi\eta$.}
    \label{fig:mbc_deltae}
\end{center}   
\end{figure}


The $B_{s}$ and $B_{s}^{*}$ masses can be extracted from the $M_{\rm bc}$ fits in the 
$B_{s}^{*}\bar{B}_{s}^{*}$ channel.
The $M_{\rm bc}$ distribution for this channel (Figure~\ref{fig:mbc}a) is obtained choosing candidates
within the $-0.08 < \Delta E < -0.02$ MeV range. 
The distribution, shown in Figure~\ref{fig:mbc}a, is fitted by the
sum of a Gaussian to describe the signal and the ARGUS function to describe the background. 
The fit yields the mass value 
$M(B_{s}^{*}) = 5418\pm  1~\mbox{MeV}/c^{2}$.
The observed width of the $B_{s}$ signal is $3.6\pm 0.6~\mbox{MeV}/c^{2}$ and 
agrees with the value obtained from the MC simulation.
Using events from the $B_{s}^{*}\bar{B}_{s}^{*}$ channel we can obtain also the 
$B_{s}$ mass (Figure~\ref{fig:mbc}b).
The distribution shown in Figure~\ref{fig:mbc}b is fitted to the sum of a Gaussian 
and the ARGUS function.
The fit yields the $B_{s}$ mass 
$M(B_{s}) = 5370\pm  1\pm  3~\mbox{MeV}/c^{2}$ and width 
$\sigma(B_{s}) = 3.6\pm  0.6~\mbox{MeV}/c^{2}$.

% --------------------------------------------------
\begin{figure}
\begin{center}
 \includegraphics[width=55mm]{fig4a.eps}
 \includegraphics[width=55mm]{fig4b.eps}
\caption{The $B_{s}^{*}$ (a) and $B_{s}$ (b) mass distributions for events within the
  $-0.08 < \Delta E < -0.02$ MeV interval, corresponding to the $B_{s}^{*}\bar{B}_{s}^{*}$ channel.}
    \label{fig:mbc}
\end{center}   
\end{figure}


Additionally, we searched for several $B_{s}$ rare decays for the first time: 
the penguin decay $B_{s}\rightarrow K^+K^-$, the electromagnetic penguin decay 
$B_{s}\rightarrow\phi\gamma$, and the intrinsic penguin decay $B_{s}\rightarrow\gamma\gamma$. 
We also searched for the tree decay
$B_{s}\rightarrow D_{s}^{(*)+}D_{s}^{(*)-}$, which is not yet observed and 
is of special interest because the $D_{s}^{(*)+}D_{s}^{(*)-}$ states are expected to be 
dominantly CP eigenstates. Although the
branching fractions for these decays are expected to be too low for observation in
this analysis, we obtained upper limits (Table~\ref{tab:upper_limit}).


\begin{table}
  \renewcommand{\baselinestretch}{1.3}
    \begin{tabular}{|c|c|c|c|c|} \hline
Decay mode  & Yield  & Background & Eff.  & upper limit\\
            &events  &events       & (\%)         &($\times 10^{-4}$)\\
\hline
$B_{s}\rightarrow K^+K^-$                 &$2$    &$0.14$   &$9.5$     &$3.4$\\\hline
$B_{s}\rightarrow\phi\gamma$              &$1$    &$0.15$   &$5.9$     &$4.1$\\\hline
$B_{s}\rightarrow\gamma\gamma$            &$0$    &$0.5$    &$20.0$    &$0.56$\\\hline
$B_{s}\rightarrow D_{s}^{+}D_{s}^{-}$     &$0$    &$0.02$   &$0.020$   &$710$\\\hline
$B_{s}\rightarrow D_{s}^{*+}D_{s}^{-}$    &$1$    &$0.01$   &$0.0090$   &$1270$\\\hline
$B_{s}\rightarrow D_{s}^{*+}D_{s}^{*-}$   &$0$    &$<0.01$   &$0.0052$   &$2730$\\\hline
    \end{tabular}
    \caption{The number of events in the signal region, estimated background events and upper limits on the $90\%$ confidence
    level for $B_{s}\rightarrow K^+K^-$, $B_{s}\rightarrow\phi\gamma$, $B_{s}\rightarrow\gamma\gamma$ and 
    $B_{s}\rightarrow D_{s}^{(*)+}D_{s}^{(*)-}$ decay modes.}
   \label{tab:upper_limit}
\end{table}



% If you have acknowledgments, this puts in the proper section head.
\bigskip % extra skip inserted
\begin{acknowledgments}
The author wish to thank the KEKB accelerator group for the excellent operation of the KEKB
accelerator.
\end{acknowledgments}

\bigskip % extra skip inserted
% Create the reference section using BibTeX:



%\bibliography{basename of .bib file}
%\begin{thebibliography}{9}   % Use for  1-9  references
\begin{thebibliography}{99} % Use for 10-99 references

%\bibitem{conjugate}
%Charge conjugate states are implied throughout the paper.

\bibitem{Eidelman:2004wy}
S.~Eidelman {\it et al.} (Particle Data Group),
%``Review of particle physics,''
Phys.\ Lett.\ B {\bf 592}, 1 (2004).

%\bibitem{HFAG}
%E.~Barberio {\it et al.} (Heavy Flavor Averaging Group), hep-ex/0603003. 

%\bibitem{Gray:2005ad}
%A.~Gray {\it et al.} (HPQCD Collaboration),
%Phys.\ Rev.\ Lett.\  {\bf 95}, 212001 (2005).
%See also S.~Hashimoto, Int.\ J.\ Mod.\ Phys.\ {\bf A 20}, 5133 (2005),
%which quotes an average value of $0.189\pm 0.027$ GeV.

\bibitem{Hou:1992sy}
W.~S.~Hou,
%``Enhanced charged Higgs boson effects in B- $\to$ tau anti-neutrino, mu
%anti-neutrino and b $\to$ tau anti-neutrino + X,''
Phys.\ Rev.\ D {\bf 48}, 2342 (1993).

\bibitem{Aubert:2005}
B.~Aubert  (BABAR Collaboration),
Phys.\ Rev.\ D {\bf 73}, 057101 (2006).


\bibitem{Falk:2000ga}
  A.~F.~Falk and A.~A.~Petrov,
  %``Measuring gamma cleanly with CP-tagged B/s and B/d decays,''
  Phys.\ Rev.\ Lett.\  {\bf 85}, 252 (2000).

\bibitem{Atwood:2001js}
  D.~Atwood and A.~Soni,
  %``Using imprecise tags of CP eigenstates in B/s and the determination of  the
  %CKM phase gamma,''
  Phys.\ Lett.\ B {\bf 533}, 37 (2002).

\bibitem{Lovelock:1985nb}
  D.~M.~J.~Lovelock {\it et al.},
  %``Masses, Widths, And Leptonic Widths Of The Higher Upsilon Resonances,''
  Phys.\ Rev.\ Lett.\  {\bf 54} 377 (1985).

\bibitem{Besson:1984bd}
  D.~Besson {\it et al.}  (CLEO Collaboration),
  %``Observation Of New Structure In The E+ E- Annihilation Cross-Section Above
  %B Anti-B Threshold,''
  Phys.\ Rev.\ Lett.\  {\bf 54}, 381 (1985).
 
\bibitem{Lee-Franzini:1990gy}
  J.~Lee- Franzini {\it et al.},
  %``Hyperfine Splitting Of B Mesons And B(S) Production At The Upsilon (5s),''
  Phys.\ Rev.\ Lett.\  {\bf 65} 2947 (1990).


\bibitem{belle_detector:2003}
A.~Abashian {\it et al.} (Belle Collaboration), 
Nucl.\ Instrum.\ Methods\ Phys.\ Res.,\ Sect.\ A {\bf 479}, 117 (2002).

\bibitem{GEANT}
R.~Brun {\it et al.},
GEANT3.21,~CERN Report DD/EE/84-1 (1984).

\bibitem{EvtGen}
See the EvtGen package home page,\\
http://www.slac.stanford.edu/\~{ }lange/EvtGen/.

%\bibitem{Albrecht:1986nr}
%H.~Albrecht {\it et al.}  (ARGUS Collaboration),
%%``Reconstruction Of B Mesons,''
%Phys.\ Lett.\ B {\bf 185}, 218 (1987).

%\bibitem{Bloom:1983pc}
%E.~D.~Bloom and C.~Peck,
%``Physics With The Crystal Ball Detector,''
%Ann.\ Rev.\ Nucl.\ Part.\ Sci.\  {\bf 33}, 143 (1983).


%\bibitem{Lyons:1988rp}
%L.~Lyons, D.~Gibaut and P.~Clifford,
%%``How To Combine Correlated Estimates Of A Single Physical Quantity,''
%Nucl.\ Instrum.\ Meth.\ A {\bf 270}, 110 (1988).

\end{thebibliography}


\end{document}
%
% ****** End of file template.aps ******

hep-ex0605068.extracted_bib
\begin{thebibliography}{9}   % Use for  1-9  references
\begin{thebibliography}{99} % Use for 10-99 references

%\bibitem{conjugate}
%Charge conjugate states are implied throughout the paper.

\bibitem{Eidelman:2004wy}
S.~Eidelman {\it et al.} (Particle Data Group),
%``Review of particle physics,''
Phys.\ Lett.\ B {\bf 592}, 1 (2004).

%\bibitem{HFAG}
%E.~Barberio {\it et al.} (Heavy Flavor Averaging Group), hep-ex/0603003. 

%\bibitem{Gray:2005ad}
%A.~Gray {\it et al.} (HPQCD Collaboration),
%Phys.\ Rev.\ Lett.\  {\bf 95}, 212001 (2005).
%See also S.~Hashimoto, Int.\ J.\ Mod.\ Phys.\ {\bf A 20}, 5133 (2005),
%which quotes an average value of $0.189\pm 0.027$ GeV.

\bibitem{Hou:1992sy}
W.~S.~Hou,
%``Enhanced charged Higgs boson effects in B- $\to$ tau anti-neutrino, mu
%anti-neutrino and b $\to$ tau anti-neutrino + X,''
Phys.\ Rev.\ D {\bf 48}, 2342 (1993).

\bibitem{Aubert:2005}
B.~Aubert  (BABAR Collaboration),
Phys.\ Rev.\ D {\bf 73}, 057101 (2006).


\bibitem{Falk:2000ga}
  A.~F.~Falk and A.~A.~Petrov,
  %``Measuring gamma cleanly with CP-tagged B/s and B/d decays,''
  Phys.\ Rev.\ Lett.\  {\bf 85}, 252 (2000).

\bibitem{Atwood:2001js}
  D.~Atwood and A.~Soni,
  %``Using imprecise tags of CP eigenstates in B/s and the determination of  the
  %CKM phase gamma,''
  Phys.\ Lett.\ B {\bf 533}, 37 (2002).

\bibitem{Lovelock:1985nb}
  D.~M.~J.~Lovelock {\it et al.},
  %``Masses, Widths, And Leptonic Widths Of The Higher Upsilon Resonances,''
  Phys.\ Rev.\ Lett.\  {\bf 54} 377 (1985).

\bibitem{Besson:1984bd}
  D.~Besson {\it et al.}  (CLEO Collaboration),
  %``Observation Of New Structure In The E+ E- Annihilation Cross-Section Above
  %B Anti-B Threshold,''
  Phys.\ Rev.\ Lett.\  {\bf 54}, 381 (1985).
 
\bibitem{Lee-Franzini:1990gy}
  J.~Lee- Franzini {\it et al.},
  %``Hyperfine Splitting Of B Mesons And B(S) Production At The Upsilon (5s),''
  Phys.\ Rev.\ Lett.\  {\bf 65} 2947 (1990).


\bibitem{belle_detector:2003}
A.~Abashian {\it et al.} (Belle Collaboration), 
Nucl.\ Instrum.\ Methods\ Phys.\ Res.,\ Sect.\ A {\bf 479}, 117 (2002).

\bibitem{GEANT}
R.~Brun {\it et al.},
GEANT3.21,~CERN Report DD/EE/84-1 (1984).

\bibitem{EvtGen}
See the EvtGen package home page,\\
http://www.slac.stanford.edu/\~{ }lange/EvtGen/.

%\bibitem{Albrecht:1986nr}
%H.~Albrecht {\it et al.}  (ARGUS Collaboration),
%%``Reconstruction Of B Mesons,''
%Phys.\ Lett.\ B {\bf 185}, 218 (1987).

%\bibitem{Bloom:1983pc}
%E.~D.~Bloom and C.~Peck,
%``Physics With The Crystal Ball Detector,''
%Ann.\ Rev.\ Nucl.\ Part.\ Sci.\  {\bf 33}, 143 (1983).


%\bibitem{Lyons:1988rp}
%L.~Lyons, D.~Gibaut and P.~Clifford,
%%``How To Combine Correlated Estimates Of A Single Physical Quantity,''
%Nucl.\ Instrum.\ Meth.\ A {\bf 270}, 110 (1988).

\end{thebibliography}