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%\section*{\Large{Introduction}}

The first meeting of the International Review Committee appointed by INFN to review the \superb\ project resulted in several detailed questions concerning the physics capability of \superb\ being posed. The \superb\ CDR discussed the physics objectives of the enterprise in some depth; these additional questions were thus meant to elucidate particular areas of interest to the committee members.

In order to prepare a coherent response, the proponents convened the Sixth \superb\ Workshop at the IFIC in Valencia, Spain from January 7-15, 2008. Organizational details and the presentations made at the workshop can be accessed at {\small https://agenda.infn.it/conferenceDisplay.py?confId=308}.  The workshop was organized into several working groups.  This document comprises the reports from these groups.

The motivation for undertaking a new generation of \epem experiments is, of course, to measure effects of New Physics on the decays of heavy quarks and leptons. A detailed picture of the observed pattern of such effects will be crucial to gaining an understanding of any New Physics found at the LHC. As detailed herein, much of the study of the capability of the LHC to distinguish between, for example, models of supersymmetry breaking have emphasized information accessible at high $p_{\rm T}$.  Many of the existing constraints on models of New Physics, however, come from flavor physics. Improving limits and teasing out new effects in the flavor sector will be just as important in constraining models after New Physics has been found as it has been in the construction of viable candidate models in the years before LHC operation.

In confronting New Physics effects on the weak decays of $b$, $c$ quarks and $\tau$ leptons, however, it is crucial to have the appropriate experimental sensitivity. The experiment must measure \CP asymmetries, rare branching fractions and interesting kinematic distributions to sufficient precision to make manifest the expected effects of New Physics, or to place constraining limits.  There is a strong consensus  in the community that doing so requires a data sample corresponding to an integrated luminosity of 50 to 100 \invab.  There is also a consensus that a reasonable benchmark for obtaining such a data sample is of the order of five years of running. Meeting both these constraints requires a collider  luminosity of \hbox{$10^{36}$ cm$^{-2}$s$^{-1}$} or more. It is these boundary conditions that set the luminosity of \superb.

Reaching this luminosity with a conventional collider design extrapolated from \pepii or KEKB is difficult; beam currents and thus power consumption are very high, and the resulting detector backgrounds are formidable. The crabbed waist design of \superb\ provides an elegant solution to the problem; \superb\ can reach unprecedented luminosity with beam currents and power consumption comparable to those at \pepii.  The test of the crabbed waist concept, presently underway at Frascati, is proceeding very well. More remains to be done, but it has already been demonstrated that beam sizes at collision can be reduced and luminosity thereby increased, with no sacrifice in specific luminosity.
%Note that the crab cavity insertion under study at KEKB, with more than an order of magnitude more resources, has yet to produce a similar %demonstration of its effectiveness.
A brief report on the crabbed waist experiments is in preparation.


The different peak luminosities of \superb\ and SuperKEKB result in quite different physics capabilities. Aside from higher luminosity at much lower power consumption, \superb\ also offers a polarized electron beam and is capable of running at lower center-of-mass energies, both of which significantly increase the physics reach of the project. The rest of this section is devoted to a succinct comparison between the physics capabilities of \superb\ and SuperKEKB.  Any such comparison is perforce difficult, especially when provided by the proponents of one of the proposed projects. To improve the precision of the comparison, let us list a few of the salient characteristics of the two collider projects as proposed

\begin{itemize}
\item \superb\ has an initial luminosity of \hbox{$10^{36}$ cm$^{-2}$s$^{-1}$}, and can therefore integrate 15 ab$^{-1}$ in a Snowmass Year of $10^7$ seconds. SuperKEKB, as embodied in the KEK Roadmap, will have a luminosity of $2\times 10^{35}$ cm$^{-2}$s$^{-1}$ and can thus integrate approximately 2 ab$^{-1}$ in the 200 days of running specified, assuming the same overall efficiency.
\item
\superb\ has a proposed upgrade path that can raise the peak luminosity to $2.5\times 10^{36}$ cm$^{-2}$s$^{-1}$. \hbox{SuperKEKB} has the potential of reaching \hbox{$8 \times 10^{35}$ cm$^{-2}$s$^{-1}$} by 2027, but this substantial upgrade is not included in the KEK Roadmap.
\item
The power consumption of \superb is 17 MW. The power consumption of SuperKEKB, which uses much higher beam currents to produce smaller luminosity, is much higher. We can find no documentation on the SuperKEKB  power consumption at $2\times 10^{35}$, but the consumption at $4 \times 10^{35}$ is quoted as 60 MW for RF alone.
\item
These higher currents produce very difficult detector backgrounds at SuperKEKB. While adequate solutions have apparently been found for luminosities in the $10^{35}$ regime, systems that can accommodate the rates at higher luminosities and are sufficiently radiation-hard have not been developed. With the crabbed waist design at \superb\ currents are comparable to those at \pep2 and backgrounds are a much less difficult issue. There are luminosity-associated backgrounds as well as current-associated backgrounds; these are currently under detailed study.
\item
It appears that $\tau$ physics will assume great importance as a probe of physics beyond the Standard Model. \superb\ includes in the baseline design an 85\% longitudinally polarized electron beam and spin rotators to facilitate the production of polarized $\tau$ pairs. This polarization is the key to the study of the structure of lepton-flavor-violating couplings in $\tau$ decay, as well as the search for a $\tau$ EDM, or for $\CP$ violation in $\tau$ decay. SuperKEKB does not incorporate a polarized beam.
\item
The recent observation of large \DzDzb mixing raises the exciting possibility of finding $\CP$ violation in charm decay, which would almost certainly indicate physics beyond the Standard Model. \superb can attack this problem in a comprehensive manner, with high luminosity data sample in the \FourS region and at the $\psi(3770)$ resonance, as the collider is designed to run at lower center-of-mass energies, at reduced luminosity. With very short duration low energy runs, a data sample an order of magnitude greater than that of the final BES-III sample can readily be obtained. SuperKEKB cannot run at low energies.
\end{itemize}

With these machine parameters and characteristics in mind, we will now compare the physics capabilities of \superb\ and SuperKEKB in several specific areas:
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\input{Comparison/B-comp}


\input{Comparison/Charm-comp}


\input{Comparison/Tau-comp}


\input{Comparison/Spectroscopy-comp}

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\begin{thebibliography}{99}

\bibitem{Bona:2007qt}
  M.~Bona {\it et al.},
  %``SuperB: A High-Luminosity Asymmetric e+ e- Super Flavor Factory. Conceptual
  %Design Report,''
  arXiv:0709.0451 [hep-ex].
  %%CITATION = ARXIV:0709.0451;%%
%\cite{Browder:2007gg}
\bibitem{Browder:2007gg}
  T.~Browder, M.~Ciuchini, T.~Gershon, M.~Hazumi, T.~Hurth, Y.~Okada and A.~Stocchi,
  %``On the Physics Case of a Super Flavour Factory,''
  JHEP {\bf 0802} (2008) 110
  [arXiv:0710.3799 [hep-ph]].
  %%CITATION = JHEPA,0802,110;%%
%\cite{Browder:2008em}
\bibitem{Browder:2008em}
  T.~E.~Browder, T.~Gershon, D.~Pirjol, A.~Soni and J.~Zupan,
  %``New Physics at a Super Flavor Factory,''
  arXiv:0802.3201 [hep-ph].
  %%CITATION = ARXIV:0802.3201;%%

\end{thebibliography}


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