TESLA Technical Design Report, Part VI, Chapter 1: The Photon Collider at TESLA
TESLA Technical Design Report, Part VI, Chapter 1: The Photon Collider at TESLA
hep-ex↗
arXiv subjects
K. Hagiwara
Publications and source records attributed to K. Hagiwara.
TESLA Technical Design Report Part III: Physics at an e+e- Linear Collider
The TESLA Technical Design Report Part III: Physics at an e+e- Linear Collider
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Prospects of Very Long Base-Line Neutrino Oscillation Experiments with the JAERI-KEK High Intensity Proton Accelerator
In this paper, we discuss physics potential of the Very Long Base-Line (VLBL) Neutrino-Oscillation Experiments with the High Intensity Proton Accelerator (HIPA), which is planned to be built by 2006 in Tokaimura, Japan. We propose to use conventional narrow-band ν_μbeams (NBB) from HIPA for observing the ν_μ\to ν_e transition probability and the ν_μsurvival probability. The pulsed NBB allows us to obtain useful information through counting experiments at a huge water-Cherenkov detector which may be placed in our neighbor countries. We study sensitivity of such an experiment to the neutrino mass hierarchy, the mass-squared differences, the mixing angles and the CP phase of the 3\times 3 lepton flavor mixing matrix (MNS matrix). The CP phase can be measured with a 100kt detector if both the mass-squared difference and U_{e3} elements of the MNS matrix are sufficiently large.
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Gold-plated processes at photon colliders
We review the most important topics and objectives of the physics program of the gamma-gamma, gamma-electron collider (photon collider) option for an e+e- linear collider.
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Prospects of Measuring General Higgs Couplings at e^+e^- Linear Colliders
We examine how accurately the general HZV couplings, with V=Z,gamma, may be determined by studying e^+e^- --> Hff-bar processes at future e^+e^- linear colliders. By using the optimal-observable method, which makes use of all available experimental information, we find out which combinations of the various HZV coupling terms may be constrained most efficiently with high luminosity. We also assess the benefits of measuring the tau-lepton helicities, identifying the bottom-hadron charges, polarizing the electron beam and running at two different collider energies. The HZZ couplings are generally found to be well constrained, even without these options, while the HZ-gamma couplings are not. The constraints on the latter may be significantly improved by beam polarization.
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Constraints on the mSUGRA parameter space from electroweak precision data
We place constraints on the parameter space of the minimal supergravity (SUGRA) inspired supersymmetric (SUSY) extension of the standard model (SM), i.e. the mSUGRA model, by studying the loop-level contributions of supersymmetric particles to electroweak precision observables. In general the Higgs and superpartner particles of SUSY models contribute to electroweak observables through universal propagator corrections as well as process-specific vertex and box diagrams. However, because the mass of the lightest chargino is contrained to be greater than 91 GeV, we find that the process-dependent contributions to four-fermion amplitudes are negligibly small. Hence, the full analysis may be reduced to an analysis of the propagator corrections, and in some regions of parameter space the constraints from the (b ---> s gamma) process are quite important. The propagator corrections are dominated by the contributions of the scalar fermions, and we summarize the results in the Peskin-Takeuchi S-T plane and the contributions to the W-boson mass. We then present the results in the mSUGRA m_0 -- m_{1/2} plane and find that our analysis of the propagator corrections provides constraints in the small-m_0 -- small-m_{1/2} region, precisely the region of interest for collider phenomenology. In some regions of parameter space, especially for mu < 0 and large tan(beta), the constrained region is enlarged considerably by including the process (b ---> s gamma).
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Quark and Lepton Flavor Mixings in the SU(5) Grand Unification Theory
We explain the imbalance of the flavor mixing angles between the quark and the lepton sectors in the context of the SU(5) GUT with the see-saw mechanism. The quark masses and the CKM matrix elements are obtained by using, respectively, the Fritzsch and Branco - Silva-Marcos form for the up- and down-quark Yukawa matrices (y^u and y^d) at the GUT scale. The charged-lepton Yukawa matrix (y^e) is the transpose of y^d, modified by the Georgi-Jarlskog factor. We show that the neutrino masses and mixing angles suggested by the recent solar and atmospheric neutrinos are then obtained from a simple texture of the neutrino Yukawa matrix (y^ν) and a diagonal right-handed Majorana mass matrix at the GUT scale.
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Searching for H --> tau tau in weak boson fusion at the LHC
Weak boson fusion is a copious source of intermediate mass Higgs bosons at the LHC. The additional very energetic forward jets in these events provide for powerful background suppression tools. We analyze the $H \to ττ$ decay mode for the Standard Model Higgs boson. A parton level analysis of the dominant physics backgrounds (mainly $Z \to ττ$ and Drell-Yan production of $τ$'s) and of reducible backgrounds (from $W+$ jet and $b\bar{b}$ production in association with two jets and subsequent leptonic decays) demonstrates that this channel allows the observation of $H \to ττ$ in a low background environment, yielding a significant Higgs signal with an integrated luminosity of about 30 fb$^{-1}$. The weak boson fusion process thus allows direct measurement of the $Hττ$ coupling.
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Global Study of Electron-Quark Contact Interactions
We perform a global fit of data relevant to $eeqq$ contact interactions, including deep inelastic scattering at high $Q^2$ from ZEUS and H1, atomic physics parity violation in Cesium from JILA, polarized $e^-$ on nuclei scattering experiments at SLAC, Mainz and Bates, Drell-Yan production at the Tevatron, the total hadronic cross section $σ_{had}$ at LEP, and neutrino-nucleon scattering from CCFR. With only the new HERA data, the presence of contact interactions improves the fit compared to the Standard Model. When other data sets are included, the size of the contact contributions is reduced and the overall fit represents no real improvement over the Standard Model.
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CP Violation at Electron-Positron Colliders
A detailed, model-independent study of CP violation at present and future electron-positron colliders is reported. Firstly, we investigate CP violation effects in $W$ boson and $t$ quark pair production in $e^+e^-$ annihilation and in two-photon fusion at a next $e^+e^-$ linear collider, where Compton-backscattered laser light off the electrons or positrons are employed as a powerful polarized photon source. Secondly, noting that there do not exist any direct measurements for the tau-lepton electric dipole moment (EDM), we address the importance of performing its direct measurements at $e^+e^-$ collisions off the Z-boson pole at TRISTAN, LEPII and CLEOII. We present a rough comparison of the potential of these experiments in the $τ$ EDM measurements. Finally, we report on our recent works for probing CP violation in the semileptonic decays of the tau lepton, which involve two different intermediate resonances with large ratios of widths to masses, and which can be most efficiently identified at the planned $B$ and proposed $τ$-charm factories. All the CP-violation phenomena in the processes under consideration, if discovered, imply new CP-violation mechanisms completely different from the Standard Model CP violation mechanism through the complex phase of the Cabibbo-Kobayashi-Maskawa matrix.
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Contact Interactions and high-Q2 events in e^+ p collisions at HERA
We consider $e e q q$ contact interactions as a possible origin of an excess of events above Standard Model predictions in $e^+ p \to e^+ jet$ at high $Q^2$ observed by the H1 and ZEUS collaborations at HERA. The HERA data prefer chirality RL or LR contact terms and atomic physics parity violation measurements severely limit parity-odd contact terms. With equal left-right and right-left chirality interactions at an effective scale of order 3 TeV we are able to reproduce the main features of the HERA data and still be consistent with Drell-Yan pair production at the Tevatron and hadron production at LEP 2 and TRISTAN.
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Probing nonstandard bosonic interactions via W-boson pair production at lepton colliders
The process e+e- --> W+W- provides a valuable laboratory to test the Standard Model (SM) and to search for new physics. The most general helicity amplitudes for this process require the introduction of nine form-factors which we calculate in the context of SU(2) X U(1) gauge-invariant extensions of the SM. The contributions of new physics are parametrized via an effective Lagrangian constructed from the light fields. Because the mechanism of electroweak symmetry-breaking remains an open problem we consider both the effective Lagrangian with a linearly realized Higgs sector, i.e. with a light physical Higgs boson, and the effective Lagrangian which utilizes a nonlinear realization of the Higgs mechanism. The use of an effective Lagrangian allows one to calculate consistently nonstandard contributions to e+e- --> W+W- amplitudes as well as the nonstandard contributions to other processes. We study the interplay of the low-energy and Z-pole measurements with measurements via the processes e+e- --> fermion pairs and e+e- --> W+W- at LEP II or a future linear e+e- collider. Concrete relationships between operators of the linear and nonlinear realizations are presented where possible.
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One Loop Supersymmetric QCD Radiative Corrections to the top quark production in $p\bar{p}$ collisions
The purpose of this note is to give the one loop radiative corrections to the top quark pair production in the $p\bar{p}$ annihilation at the Fermilab Tevatron in the context of the Minimal Supersymmetric Model. We concentrate here on the supersymmetric QCD corrections and give the analytic expression for these corrections. Recently Li et. al. have reported the supersymmetric QCD corrections to this process we indicate clearly a comparison of their and our work. In particular, we find additional corrections [crossed box and gluon self-energy] at the one loop level which are not given by Li et. al.. Our numerical results disagree with the original claim of Li et. al. The numerical values given by them in a recent erratum do agree with the general trend of our numerical results however the actual values still disagree. We find that the percentage corrections at the hadronic corrections changes from $22\%$ to $-0.5\%$ as the squark mass is changed from 100 GeV to 600 GeV, for a gluino mass of 200 GeV. For a gluino mass of 150 GeV the squark-mass dependence is less abrupt; they change from $-5.3\%$ to $1\%$ as the squark mass is varied between 100 GeV and 600 GeV. We also present numerical results for differential cross section at the hadronic level, and percentage corrections at the parton level. PACS number(s): 14.80Dq; 12.38Bx; 14.80. Gt
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Probing CP Violation in $γγ\to W^+W^-$ with Polarized Photon Beams
We demonstrate in a general framework that polarized photons by backscattered laser beams of adjustable frequencies at a TeV linear $e^+e^-$ collider provide us with a very efficient mechanism to probe CP violation in two-photon collisions. CP violation in the process $γγ\rightarrow W^+W^-$ is investigated in detail with linearly polarized photon beams. There are two useful CP-odd asymmetries that do not require detailed information on $W$ decay products. The sensitivity to the CP-odd form factors are studied quantitatively by assuming a perfect $e$-$γ$ conversion and the 20 fb$^{-1}$ $e^+e^-$ integrated luminosity at the $e^+e^-$ c.m. energies $\sqrt{s}=0.5$ and $1.0$ TeV. The sensitivity is so high that such experiments will allow us to probe new CP violation effects beyond the limits from some specific models with reasonable physics assumptions. We find that a counting experiment of $W^+W^-$ events in the two-photon mode with adjustable laser frequencies can have much stronger sensitivity to the CP-odd $γ(γ) WW$ form factors than can a $W^+W^-$ decay-correlation experiment with a perfect detector achieve in the $e^+e^-$ mode. PACS number(s): 14.70.Bh, 14.70.Hp, 13.88.+e
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Supersymmetric contribution to the quark-lepton universality violation in charged currents
The supersymmetric one-loop contribution to the quark-lepton universality violation in the low-energy charged current weak interactions is studied. It is shown that the recent experimental data with the 1-$σ$ deviation from the universality may be explained by the existence of the light sleptons ($<220$GeV) and relatively light chargino and neutralinos ($<600$GeV) with significant gaugino components. The sign of the universality violation is briefly discussed.
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Probing the Top-Quark Electric Dipole Moment at a Photon Linear Collider
We probe the top-quark electric dipole moment (EDM) in top-quark pair production via photon-photon fusion at a photon linear collider. We show how linearly-polarized photon beams can be used to extract information on the top-quark EDM without the use of complicated angular correlations of top-quark decay products. If the luminosity of the laser back-scattered photon-photon collisions is comparable to that of the $e^+e^-$ collisions, then the measurement of the top-quark EDM obtained by counting top-quark-production events in photon fusion can be as accurate as the measurement obtained by studying the $t\bar{t}$ decay correlations in $e^+e^-$ collisions using a perfect detector.
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Constraints on New Physics in the Electroweak Bosonic Sector from Current Data and Future Experiments
Extensions of the Standard Model which involve a new scale, $Λ$, may, for energies sufficiently small compared to this new scale, be expressed in terms of operators with energy dimension greater than four. The coefficients of just four SU(2)$\times$U(1)-gauge-invariant energy-dimension-six operators are sufficient to parameterize the contributions of new physics in the electroweak bosonic sector to electroweak precision measurements. In this letter we update constraints on the coefficients of these four operators due to recent precision measurements of electroweak observables. We further demonstrate how such constraints may be improved by experiments at TRISTAN, LEP2 and at a future linear $e^+e^-$ collider. The relationship of these operators to the oblique parameters $S$, $T$ and $U$ is examined. Two of the operators contribute to a non-standard running of the electroweak charge form-factors $\overlineα(q^2)$, $\overline{s}^2(q^2)$, $\overline{g}_Z^2(q^2)$ and $\overline{g}_W^2(q^2)$; in the special case where the coefficients of these two vanish the operator analysis reduces to an analysis in terms of $S$, $T$ and $U$ with $U = 0$.
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CP Violation in $τ\rightarrow 3πν_τ$
We consider CP violating effects in the decays $τ\rightarrow (3π)ν_τ$ where both the ${\rm J}^{\rm P}=1^+$ resonance, $a_1$, and ${\rm J}^{\rm P}=0^-$ resonance, $π^\prime$, can contribute. The interference between the $a_1$ and $π^\prime$ resonances can lead to enhanced CP-violating asymmetries whose magnitudes depend crucially on the $π^\prime$ decay constant, $f_{π^\prime}$. We make an estimate of $f_{π^\prime}$ with a simplified chiral Lagrangian coupled to a massive pseudoscalar field, and we compare the estimates from the non-relativistic quark model and from the QCD sum rule with the estimate from the `mock' meson model. We then estimate quantitatively the size of CP-violating effects in a multi-Higgs-doublet model and scalar-leptoquark models. We find that, while CP-violating effects in the scalar-leptoquark models may require more than $10^{10}$ $τ$ leptons, CP-violating effects from the multi-Higgs-doublet model can be seen at the $2σ$ level with about $10^7$ $τ$ leptons using the chiral Lagrangian estimate of $f_{π^\prime}=(1\sim 5)\times 10^{-3}$ GeV.
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