2a3 > 11a13 > 17a20 > 18a22 > 26a31 > 27a33 > 41a48 > 47a55 > 53a62 > 73a83 > 74a85 > 101a113 > 131a144 > 203a217 > 224a239 > 229a245 > 230a247 > 241a259 > 247a266 > 255a275 > 264a285 > 272a294 > 283a306 > 294a318 > 299a324 > 319a345 > 351a378 > 357a385 > 371a400 > 399a429 > 428a459,460 > > 429a462 > 499a533 > 505a540 > 519a555 > 554a591 > 559a597 > 560a599 > 622a662 > 637a678 > 653a695 > 655a698,699 > > 656a701 > 678a724,725 > > 698a746 > 746a795 > 774a824 > 776,778c826,1046 < \input{non_osci.tex} < %% < %% --- > > \subsection{Non-oscillation physics at a Neutrino Factory} > > The study of the utility of intense neutrino beams from a muon storage ring in > determining the parameters governing non-oscillation physics was begun > in 1997~\cite{rajageer}. More complete studies can be found in~\cite{INTRO:ref9} and recently a European group has brought out an > extensive study on this topic~\cite{cern-nonosc}. > > A Neutrino Factory can measure individual parton distributions within the > proton for all light quarks and anti-quarks. > It could improve valence distributions > by an order of magnitude in the kinematical range $x\gsim 0.1$ in the > unpolarized case. > The individual components of the sea ($\bar{u}$, $\bar{d}$, ${s}$ and > $\bar{s}$), as well as the gluon, would be measured with relative > accuracies in the range of 1--10\%, for $0.1\lsim x \lsim 0.6$. A > full exploitation of the Neutrino Factory > potential for polarized measurements of the shapes of > individual partonic densities requires an {\it a priori} knowledge of > the polarized gluon density. > The forthcoming set of polarized deep inelastic scattering > experiments at CERN, DESY and RHIC may provide > this information. > > The situation is also very bright for measurements of $C$-even > distributions. Here, the first moments of singlet, triplet and octet > axial charges can be measured with > accuracies that are up to one order of magnitude better than the > current uncertainties. In particular, the improvement in the > determination of the singlet axial charge would allow a definitive > confirmation or refutation of the anomaly scenario compared to the > `instanton' or `skyrmion' scenarios, at least if the theoretical > uncertainty originating from the small-$x$ extrapolation can be kept under > control. The measurement of the octet axial charge with a few percent > uncertainty will allow a determination of the strange contribution to > the proton spin better than 10\%, and allow stringent tests of models > of $SU(3)$ violation when compared to the direct determination from > hyperon decays. > > A measurement of $\as(M_Z)$ and > $\sin^2\theta_W$ will involve different systematics from current > measurements and will therefore provide an important consistency check of > current data, although the > accuracy of these values is not expected to be improved. > The weak mixing angle can be measured in both the hadronic and leptonic > modes with a precision of approximately > $2\times 10^{-4}$, dominated by the statistics and the luminosity > measurement. > This determination would be > sensitive to different classes of new-physics contributions. > > Neutrino interactions are a very good source of clean, sign-tagged charm > particles. A Neutrino Factory can measure charm production with raw event rates up to > 100 million charm events per year with $\simeq$ 2 million double-tagged events. > (Note that charm production becomes significant for storage ring energies > above 20~GeV). > Such large samples are suitable for precise extractions of branching ratios > and decay constants, the study of spin-transfer > phenomena, and the study of nuclear effects in deep inelastic scattering. > The ability to run with both hydrogen and > heavier targets will provide rich data sets useful for > quantitative studies of nuclear models. > The study of $\Lambda$ polarization both in the target and in the > fragmentation regions will help clarify the intriguing problem of > spin transfer. > > > Although the neutrino beam energies are well below any reasonable threshold for new physics, the large statistics makes it possible to search for > physics beyond the Standard Model. The high intensity neutrino beam allows > a search for the production and decay of neutral heavy leptons > with mixing angle sensitivity two orders of magnitude better than present > limits in the 30--80 MeV range. > The exchange of new gauge bosons > decoupled from the first generation of quarks and leptons can be seen > via enhancements of the inclusive charm production rate, with a > sensitivity well beyond the present limits. > A novel neutrino magnetic moment search technique that uses oscillating > magnetic fields at the neutrino beam source could discover large > neutrino magnetic moments predicted by some theories. > Rare lepton-flavor-violating decays of muons in the ring could be tagged > in the deep inelastic scattering final states > through the detection of wrong-sign electrons and muons, or of prompt > taus. > > \subsection{Physics that can be done with Intense Cold Muon Beams} > > Experimental studies of muons at low and medium energies have had a > long and distinguished history, starting with the first search for > muon decay to electron plus gamma-ray~\cite{Hincks-Pontecorvo}, and > including along the way the 1957 discovery of the nonconservation of > parity, in which the $g$ value and magnetic moment of the muon were > first measured~\cite{Garwinetal}. The years since then have brought > great progress: limits on the standard-model-forbidden decay $\mu\to > e\gamma$ have dropped by nine orders of magnitude, and the muon > anomalous magnetic moment $a_\mu=(g_\mu-2)/2$ has yielded one of the > more precise tests ($\approx1$ ppm) of physical theory~\cite{BNLg-2}. > > The front end of a Neutrino Factory has the potential to provide > $\sim10^{21}$ muons per year, five orders of magnitude beyond the most > intense beam currently available\footnote{The $\pi$E5 beam at PSI, > Villigen, providing a maximum rate of $10^9$ muons/s~\cite{Edgecock}.}. > Such a facility could enable precision measurements of the muon > lifetime $\tau_\mu$ and Michel decay parameters as well as sensitive > searches for lepton-flavor nonconservation (LFV), a possible ($P$- and > $T$-violating) muon electric dipole moment (EDM) > $d_\mu$~\cite{HIMUS99}, and $P$ and $T$ violation in muonic atoms. It > could also lead to an improved direct limit on the mass of the muon > neutrino~\cite{numass}. Of these possibilities, > Marciano~\cite{Marciano97} has suggested that muon LFV (especially > coherent muon-to-electron conversion in the field of a nucleus) is the > ``best bet" for discovering signatures of new physics using low-energy > muons; measurement of $d_\mu$ could prove equally exciting but is not > yet as well developed, being only at the Letter of Intent stage at > present~\cite{EDMLOI}\footnote{Experimentalists might argue that > extending such measurements as $\tau_\mu$ and the Michel parameters is > worthwhile whenever the state of the art allows substantial > improvement. However, their comparison with theory is dominated by > theoretical uncertainties. Thus, compared to Marciano's ``best bets," > they represent weaker arguments for building a new facility.}. > > The search for $\mu\to e \gamma$ is also of great interest. The MEGA > experiment recently set an upper limit $B(\mu^+\to > e^+\gamma)<1.2\times10^{-11}$~\cite{MEGA}. Ways to extend sensitivity > to the $10^{-14}$ level have been > discussed~\cite{Cooper97}. Sensitivity greater than this may be > possible but will be difficult since at high muon rate there will be > background due to accidental coincidences; a possible way around this > relies on the correlation between the electron direction and the > polarization direction using a polarized muon beam. The > $\mu$-to-$e$-conversion approach does not suffer from this drawback > and has the additional virtue of sensitivity to possible new physics > that does not couple to the photon. > > In the case of precision measurements ($\tau_\mu$, $a_\mu$, etc.), > new-physics effects can appear only as small corrections arising from > the virtual exchange of new massive particles in loop diagrams. In > contrast, LFV and EDMs are forbidden in the standard model, thus their > observation at any level constitutes evidence for new physics. The > current status and prospects for advances in these areas are > summarized in Table~\ref{tab:LEmuons}. It is worth recalling that LFV > as a manifestation of neutrino mixing is suppressed as $(\delta > m^2)^2/m_W^4$ and is thus entirely negligible. However, a variety of > new-physics scenarios predict observable effects. > Table~\ref{tab:newmuphys} lists some examples of limits on new physics > that would be implied by nonobservation of $\mu$-to-$e$ conversion > ($\mu^-N\to e^-N$) at the $10^{-16}$ level~\cite{Marciano97}. > > \begin{table} > \caption[Current and future tests in low energy muons] {Some current > and future tests for new physics with low-energy muons > (from~\protect\cite{Marciano97}, \protect\cite{PDG}, and > \protect\cite{Aoki01}). Note that the ``Current prospects" column > refers to anticipated sensitivity of experiments currently approved or > proposed; ``Future" gives estimated sensitivity with the Neutrino Factory > front end. (The $d_\mu$ measurement is still at the Letter of Intent > stage and the reach of experiments is not yet entirely > clear.)\label{tab:LEmuons}} > \begin{center} > \begin{tabular}{|lccc|} > \hline > Test & Current bound & Current prospects & Future \\ > \hline > $B(\mu^+\to e^+\gamma)$ & $<1.2\times10^{-11}$ & > $\approx5\times10^{-12}$ & $\sim10^{-14}$\\ $B(\mu^-{\rm Ti}\to > e^-{\rm Ti})$ & $<4.3\times10^{-12}$ & $\approx2\times10^{-14}$ & > $<10^{-16}$\\ $B(\mu^-{\rm Pb}\to e^-{\rm Pb})$ & $<4.6\times10^{-11}$ > & & \\ $B(\mu^-{\rm Ti}\to e^+{\rm Ca})$ & $<1.7\times10^{-12}$ & & \\ > $B(\mu^+\to e^+e^-e^+)$ & $<1\times10^{-12}$ & & \\ $d_\mu$ & > $(3.7\pm3.4)\times10^{-19}\,e\cdot$cm & $10^{-24}\,e\cdot$cm? & ? \\ > \hline > \end{tabular} > \end{center} > \end{table} > > \begin{table} > \caption[New physics probed by $\mu\rightarrow e$ experiments] > {Some examples of new physics probed by the nonobservation of > $\mu\rightarrow e$ conversion at the $10^{-16}$ level > (from~\protect\cite{Marciano97}).\label{tab:newmuphys}} > \begin{center} > \begin{tabular}{|lc|} > \hline > New Physics & Limit \\ > \hline > Heavy neutrino mixing & $|V_{\mu N}^*V_{e N}|^2<10^{-12}$\\ Induced > $Z\mu e$ coupling & $g_{Z_{\mu e}}<10^{-8}$\\ Induced $H\mu e$ > coupling & $g_{H_{\mu e}}<4\times10^{-8}$\\ Compositeness & > $\Lambda_c>3,000\,$TeV\\ > \hline > \end{tabular} > \end{center} > \end{table} > > Precision studies of atomic electrons have provided notable tests of > QED ({ e.g,}\ the Lamb shift in hydrogen) and could in principle be > used to search for new physics were it not for nuclear corrections. > Studies of muonium ($\mu^+e^-$) are free of such corrections since it > is a purely leptonic system. Muonic atoms also can yield new > information complementary to that obtained from electronic atoms. A > number of possibilities have been enumerated by Kawall {\it et > al.}~\cite{Kawall97} and Molzon~\cite{Molzon97}. As an example we > consider the hyperfine splitting of the muonium ground state, which > has been measured to 36 ppb~\cite{Mariam} and currently furnishes the > most sensitive test of the relativistic two-body bound state in > QED~\cite{Kawall97}. The precision could be further improved with > increased statistics. The theoretical error is 0.3 ppm but could be > improved by higher-precision measurements in muonium and muon spin > resonance, also areas in which the Neutrino Factory front end could > contribute. Another interesting test is the search for > muonium-antimuonium conversion, possible in new-physics models that > allow violation of lepton family number by two units. The current > limit is $R_g \equiv G_C / G_F< 0.0030$~\cite{PDG}, where $G_C$ is the > new-physics coupling constant and $G_F$ is the Fermi coupling > constant. This sets a lower limit of $\approx 1 \,$TeV$/c^2$ on the > mass of a grand-unified dileptonic gauge boson and also constrains > models with heavy leptons~\cite{Abela}. > > > > > 781a1050 > 800a1070 > 825a1096,1097 > > 838a1111 > 860a1134 > 861a1136 > 914a1190 > 943a1220 > 952a1230 > 964a1243 > 972a1252 > 973a1254 > 985a1267 > 997a1280 > 1009a1293 > 1021a1306 > 1040a1326 > 1070a1357 > 1095a1383 > 1096a1385 > 1108a1398 > 1109a1400 > 1119a1411 > 1132a1425 > 1158a1452 > 1169a1464 > 1172a1468 > 1176a1473 > 1187a1485,1487 > > >