Detector issues for a photon collider

The photon collider is an option at the ILC. In this note detector issues are discussed that are relevant for the change from the e ⁺ e ⁻ mode of the ILC to the γγ mode.      

Virtual effects of split-SUSY in Higgs productions at linear colliders

In split supersymmetry, gauginos and higgsinos are the only supersymmetric particles possibly accessible at foreseeable colliders like the CERN Large Hadron Collider (LHC) and the International Linear Collider (ILC). In order to account for the cosmic dark matter measured by WMAP, these gauginos and higgsinos are stringently constrained and could be explored at the colliders through their direct productions and/or virtual effects in some processes. The clean environment and high luminosity of the ILC render the virtual effects at percent level meaningful in unraveling the new physics effects. In this work we assume split supersymmetry and calculate the virtual effects of the WMAP-allowed gauginos and higgsinos in the Higgs productions e⁺e^-→Zh and e⁺e^-→ν_eν̄_eh through WW fusion at the ILC. We find that the production cross section of e⁺e^-→Zh can be altered by a few percent in some part of the WMAP-allowed parameter space, while the correction to the WW fusion process e⁺e^-→ν_eν̄_eh is below 1%. Such virtual effects are correlated with the cross sections of chargino pair productions and can offer complementary information in probing split supersymmetry at the colliders. PACS 14.80.Ly; 95.35.+d     

The E166 experiment: Development of an undulator-based polarized positron source for the international linear collider

A longitudinal polarized positron beam is foreseen for the international linear collider (ILC). A proof-of-principle experiment has been performed in the final focus test beam at SLAC to demonstrate the production of polarized positrons for implementation at the ILC. The E166 experiment uses a 1 m long helical undulator in a 46.6 GeV electron beam to produce a few MeV photons with a high degree of circular polarization. These photons are then converted in a thin target to generate longitudinally polarized e ⁺ and e ⁻. The positron polarization is measured using a Compton transmission polarimeter. The data analysis has shown asymmetries in the expected vicinity of 3.4% and ∼1% for photons and positrons respectively and the expected positron longitudinal polarization is covering a range from 50% to 90%.      

Distinguishing new physics scenarios with polarized electron and positron beams

Contact-like nonstandard interactions can be revealed only through deviations of observables from the standard model (SM) predictions. We consider a number of such nonstandard scenarios, and discuss their identification as sources of deviations in fermion-pair production processes at the international linear collider (ILC), if they were observed. We emphasize the role of e ⁻ and e ⁺ polarization in enhancing the identification reaches.      

The correction of the littlest Higgs model to the Higgs production process e<Superscript>+</Superscript>e<Superscript>-</Superscript>→e<Superscript>+</Superscript>e<Superscript>-</Superscript>H at the ILC

The littlest Higgs model is the most economical one among various little Higgs models. In the context of the littlest Higgs model, we study the process e⁺e^-→e⁺e^-H at the ILC and calculate the correction of the littlest Higgs model to the cross section of this process. The results show that, in the favorable parameter spaces preferred by the electroweak precision data, the value of the relative correction is in the range from a few percent to tens percent. In most cases, the correction is large enough to reach the measurement precision of the ILC. Therefore, the correction of the littlest Higgs model to the process e⁺e^-→e⁺e^-H might be detected at the ILC, which will give an ideal way to test the model. PACS 12.60.Nz; 14.80.Mz; 12.15.Lk; 14.65.Ha     

Distinguishing indirect signatures of new physics at ILC with polarized beams: Z′ versus anomalous trilinear gauge couplings

We examine the sensitivity of the e ⁺ e ^? International Linear Collider (ILC) for probing the Z-Z′ mixing in W ^±-pair production process and its capability of distinguishing observable effects of the Z′ from analogous ones due to competitor models with anomalous trilinear gauge couplings (AGC) that can lead to the same or similar new physics experimental signatures.     

Power losses in the international linear collider 20 mrad extraction line at 1 TeV

We have performed a detailed study of the power losses in the post-collision extraction line of a TeV e ⁺ e ⁻ collider with a crossing angle of 20 mrad at the interaction point. Five cases were considered: four luminosity configurations for ILC and one for CLIC. For all of them, the strong beam-beam effects at the interaction point lead to an emittance growth for the outgoing beam, as well as to the production of beamstrahlung photons and e ⁺ e ⁻ coherent pairs. The power losses along the extraction line, which are due to energy deposition by a fraction of the disrupted beam, of the beamstrahlung photons and of the coherent pairs, were estimated in the case of ideal collisions, as well as with a vertical position or angular offset at the interaction point.      

Complementarity of the CERN Large Hadron Collider and the <Emphasis Type="Italic">e</Emphasis><Superscript>+</Superscript><Emphasis Type="Italic">e</Emphasis><Superscript>−</Superscript> International Linear Collider

The next-generation high-energy facilities, the CERN Large Hadron Collider (LHC) and the prospective e ⁺ e ⁻ International Linear Collider (ILC), are expected to unravel new structures of matter and forces from the electroweak scale to the TeV scale. In this report we review the complementary role of LHC and ILC in drawing a comprehensive and high-precision picture of the mechanism breaking the electroweak symmetries and generating mass, and the unification of forces in the frame of supersymmetry. Extended version of Ref. [1] to be published in “Supersymmetry on the Eve of the LHC”, a special volume of European Physical Journal C, Particles and Fields (EPJC) in memory of Julius Wess.     

The new charged gauge boson W’ and the subprocess eq→νq’ at e+e- and ep colliders

In the framework of little Higgs models and the three-site Higgsless model, we discuss the contributions of the new charged gauge boson W’ to the process eq→νq’ and the possibility of detecting W’ via this process in future high energy linear e⁺e^- collider (ILC) and ep collider (THERA) experiments. Our numerical results show that the process eq→νq’ is rather sensitive to the coupling W’ff’, and one can use this process to distinguish different new physics models in future ILC and THERA experiments. PACS  12.60.Cn; 14.70.Pw; 14.65.Bt     

Physics at the linear collider

The physics at the plannede ⁺ e ^- colliders is discussed around three main topics corresponding to different manifestations of symmetry breaking:W physics in the no Higgs scenario, studies of the properties of the Higgs and precision tests of SUSY. A comparison with the LHC is made for all these cases. The γγ mode of the linear collider will also be reviewed.     

Precise calculations of observables of polarized møller scattering: From JLAB to ILC energies

One-loop electroweak corrections to observables of the reaction e ⁻ e ⁻ → e ⁻ e ⁻(γ) were calculated over a broad range of energies: from conditions of the MOLLER experiment at the Thomas Jefferson Laboratory (JLab) to those of planned experiments at the International Linear Collider (ILC). The dependence of various contributions to the observable polarization asymmetry on various renormalization conditions was studied within the scheme of on-shell renormalization. The results were obtained by two methods: precisely, by applying the FeynArts, FormCalc, LoopTools, and Form computer codes, and approximately, with the aid of the asymptotic-estimation methods. The resulting compact formulas are absolutely free from nonphysical parameters and are convenient for deducing numerical estimates. It is shown that the total one-loop correction is independent of renormalization conditions and takes an identical value within different computational schemes.     

Polarization effects accompanying penetration of high-energy electrons,positrons and gamma-quanta through crystals

Abstract

Synchrotron-like processes of radiation and pair production in fields of crystal planes are accompanied by large number of polarization effects. These effects can be used for production and analysis of TeV-energy polarized e ⁺, e ^?, photon and hadron beams for their use in high-energy physics. The process of e ⁺ and e ^? self-polarization accomapnies their radiation in bent crystals, where channeled particles are moving in regions having a preferential direction of the electric field. The results of numerical simulation of self-polarization process with both radiation and multiple scattering taken into account are presented. It is shown that the self-polarization process can be observed using present-day CERN secondary positron beam. At TeV-energy region the efficiency of both e ⁺ and e ^? self-polarization can be considerably risen by making the crystal curvature growing along the crystal.     

Recent KLOE results on hadron physics

The KLOE experiment at the Frascati e ⁺ e ^- collider DAFNE has completed this year its data taking. An integrated luminosity of 2.7fb^-1 has been collected mostly at the φ-resonance peak. A wide experimental program is in progress. The detection of φ radiative decays allows to study the properties of the lowest-mass scalar and pseudoscalar mesons and to obtain information on their structure. The main results are reviewed together with the prospects for low-energy e ⁺ e ^- physics at Frascati.     

Pair production of the heavy leptons in future high energy linear e<Superscript>+</Superscript>e<Superscript>-</Superscript> colliders

The littlest Higgs model with T-parity predicts the existence of the T-odd particles, which can only be produced in pairs. We consider pair production of the T-odd leptons in a future high energy linear e⁺e^- collider (ILC). Our numerical results show that, as long as the T-odd leptons are not too heavy, they can be copiously produced and their possible signals might be detected via the processes e⁺e^-→L̄_iL_j in future ILC experiments.     

Event-shape of dileptons plus missing energy at a linear collider as a supersymmetry/Arkani-Hamed-Dimopoulos-Dvali discriminant

An event-shape analysis of the dileptons in the process e ⁺ e ⁻ → ℓ⁺ℓ⁻ , studied in ILC or CLIC, can clearly discriminate between a supersymmetric or a large extra dimensional (ADD) production mechanism.      

A study of the three- and four-photon final states produced in e+e− annihilation at 35⩽s⩽46.8 GeV

The reactions e⁺e⁻→γγγ and e⁺e⁻→γγγγ have been studied at center-of-mass energies between 35 and 46.8 GeV with an integrated luninosity of about 130 pb⁻¹accumulated with the CELLO detector at PETRA. The measurements are compared to QED calculations up to third and fourth orders of perturbation theory. Excellent agreement is observed.     

Weak neutral currents in the U3(W)-gauge theory of weak and electromagnetic interactions

A discussion is given of the implications of the recently proposed U₃(W)-gauge theory of weak and electromagnetic interactions (Pandit 1976) for some phenomena resulting from its weak neutral currents: (1) neutrino-electron scattering, (2) neutrino-nucleon elastic and inelastic scattering, (3) coherent neutrino-nucleus scattering (4) weak interaction effects ine ⁺ e ⁻→μ⁺μ⁻ and (5) parity-violation in atomic physics. The theory agrees quite well with the available experimental results on neutrino processes. We find the coherent neutrino-nucleus cross-section for Fe⁵⁶ to be about 6 times larger than that in the WS-GIM theory giving some hope of accounting for supernova explosion by the resulting neutrino-radiation pressure.     

Ultimate parameters of the photon collider at the international linear collider

At linear colliders, the e ⁺ e ⁻ luminosity is limited by beam-collision effects, which determine the required emittances of beams in damping rings (DRs). In γγ collisions at the photon collider, these effects are absent, and so smaller emittances are desirable. In the present damping ring designs, nominal DR parameters correspond to those required for e ⁺ e ⁻ collisions. In this note, I would like to stress once again that as soon as we plan the photon collider mode of ILC operation, the damping ring emittances are dictated by the photon collider requirements — namely, they should be as small as possible. This can be achieved by adding more wigglers to the DRs; the incremental cost is easily justified by a considerable potential improvement of the γγ luminosity. No expert analysis exists as of now, but it seems realistic to obtain a factor five increase of the γγ luminosity compared to the ‘nominal’ DR design.      

Discriminating between Z′-boson effects and effects of anomalous gauge couplings in the double production of W ± bosons at a linear collider

The potential of the International Linear electron-positron Collider (ILC) for seeking, in the annihilation production of W ^±-boson pairs, signals induced by new neutral gauge bosons predicted by models belonging to various classes and featuring an extended gauge sector is studied. Limits that will be obtained at ILC for the parameters and masses of Z′ bosons are compared with present-day and future data from the Large Hadron Collider (LHC). The possibility of discriminating between the effects of Z-Z′ mixing and signals induced by anomalous gauge couplings (AGC) is demonstrated within theoretically motivated trilinear gauge models involving several free anomalous parameters. It is found that the sensitivity of ILC to the effects of Z-Z′ mixing in the process e ⁺ e ^? → W ⁺ W ^? and its ability to discriminate between these two new-physics scenarios, Z′ and AGC, become substantially higher upon employing polarized initial (e ⁺ e ^?) and final (W ^±) states.     

Second-order eikonal corrections for

The first-order eikonal approximation is frequently adopted in interpreting the results of A(e,e^′p) measurements. Glauber calculations, for example, typically adopt the first-order eikonal approximation. We present an extension of the relativistic eikonal approach to A(e,e^′p) which accounts for second-order eikonal corrections. The numerical calculations are performed within the relativistic optical model eikonal approximation. The nuclear transparency results indicate that the effect of the second-order eikonal corrections is rather modest, even at Q²≈0.2 (GeV/c)². The same applies to polarization observables, left–right asymmetries, and differential cross sections at low missing momenta. At high missing momenta, however, the second-order eikonal corrections are significant and bring the calculations in closer agreement with the data and/or the exact results from models adopting partial-wave expansions.