Santosh Kumar Rai
We study signals for beyond standard model physics and consider the virtues of single photon signals or associated photons in the final states in identifying different scenarios of new physics models in a very efficient and novel way.
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We calculate the total cross sections for squark production at future photon-proton and photon-electron colliders in R-parity violating MSSM. The Lambda-prime couplings offer several ways of producing single squarks at photon colliders. The results are discussed and compared with those of the existing colliders.
A study of di-jet measurements at a future photon collider is reported. The sensitivity to extract the gluon distribution is discussed. The results are compared with calculations for a linear e+e- collider.
I review the physics prospects for high energy photon photon colliders, emphasizing results presented at the LBL Gamma Gamma Collider Workshop. Advantages and difficulties are reported for studies of QCD, the electroweak gauge sector, supersymmetry, and electroweak symmetry breaking.
A (updated) summary of the Photon-Photon and Electron-Photon physics session is presented.
We study $J/Ψ$ production at photon-photon colliders, which can be realised with Compton scaterring of laser photons at $e^+e^-$ colliders. We find that the production rate through the color-octet channel is comparable to that through the color-singlet channel. Experimentally the two mechanisms can be studied separately because the processes have different signals.
We discuss the complementarity between the LHC and a low energy photon collider. We mostly consider the scenario, where the first linear collider is a photon collider based on dual beam technology like CLIC.
Photon-photon scattering at the Photon Linear Collider is considered. Explicit formulas for helicity amplitudes due to $W$ boson loops are presented. It is shown that photon-photon scattering should be easily observable at PLC and separation of the $W$ loop contribution (which dominates at high energies) will be possible at $e^+e^-$ c.m. energy of 500~GeV or higher.
Here we review potential of the Photon Collider for study of Higgs physics after discovery of the SM-like Higgs boson at the LHC. In general, the Photon Collider will fill in the LHC and ILC results, giving in some cases unique information which cannot be obtained at other machines.
In the Randall-Sundrum model there can be a rich new phenomenology associated with Higgs-radion mixing. A photon-photon collider would provide a crucial complement to the LHC and a future ILC collider for fully determining the parameters of the model and definitively testing it.
We calculate total and differential cross sections for sfermion production in $e^+e^-$ annihilation and in photon-photon collisions with arbitrary photon polarization. The total cross section at a polarized photon collider is shown to be larger than the $e^+e^-$ annihilation cross section up to the kinematic limit of the photon collider.
Prospects for QCD studies in two-photon interactions at a future linear e+e- and gamma-gamma collider are discussed.
Sensitivity to the supersymmetric scalar states $ϕ$ at the future linear $e^+e^-$ and photon colliders is discussed. In particular it is illustrated a search strategy for massive sgoldstinos, the supersymmetric partners of the goldstino.
A review of results on top quark physics expected at the Photon Linear Colliders is presented.
The physics prospects of the high energy Photon Linear Collider are reviewed, emphasizing its potential to study the symmetry breaking sector, including Higgs searches and precision anomalous W couplings measurements.
We examine the potential for detecting and studying Higgs bosons at a photon-photon collider facility associated with a future linear collider. Our study incorporates realistic $\gam\gam$ luminosity spectra based on the most probable available laser technology. Results include detector simulations. We study the cases of: a) a SM-like Higgs boson; b) the heavy MSSM Higgs bosons; c) a Higgs boson with no $WW/ZZ$ couplings from a general two Higgs doublet model.
The physics potential of a high-energy photon collider is reviewed. The emphasis is put on aspects related to the symmetry breaking sector, including Higgs searches and production of longitudinal vector bosons.
The luminosity distribution in the effective $γγ$ mass at photon collider has usually two peaks which are well separated: high energy peak with mean energy spread 5-7% and wide low energy peak.The low energy peak depends strongly on details of design it is unsuitablefor the study of New Physics phenomena. We find simple approximte form of spectra of collided photons for $γγ$ and $eγ$ colliders wich convolution describes high energy luminosity peak with good accuracy in the most essential preferable region of parameters.
We present new results from studies in progress on physics at a two-photon collider. We report on the sensitivity to top squark parameters of MSSM Higgs boson production in two-photon collisions; Higgs boson decay to two photons; radion production in models of warped extra dimensions; chargino pair production; sensitivity to the trilinear Higgs boson coupling; charged Higgs boson pair production; and we discuss the backgrounds produced by resolved photon-photon interactions.
We study the effects of heavy Higgs bosons on the top-pair production process at photon linear colliders. The interference patterns between the resonant Higgs-production amplitudes and the continuum QED amplitudes are examined. The patterns tell us not only the CP nature of the Higgs bosons but also the phase of the $γγ$--Higgs vertex which gives new information about the Higgs couplings to new charged particles.
Processes with creation of a pair charged particles with emission of hard photon and two pairs of charged particles are considered for colliding partially polarized photon photon beams. The effects of circular and linear polarization of the initial photons are discussed in more details.
Subjects of discussion Different scenarios Higgs window to a New Physics Anomalies in the interactions of gauge and Higgs bosons Some problems with t-quarks and MSSM. Some problems in QCD and hadron physics. By-product: Production of axions, etc. from region of conversion e --> gamma.
The spectrum of single-photon events detected in the forward and in the barrel region of a TESLA linear collider detector was studied in order to investigate the production of superlight Gravitino pairs associated with a photon.
The calibration QED process cross sections for experiments on planned electron-photon and photon-photon colliders for detecting the small angles scattered particles are calculated. These processes describe the creation of two jets moving sufficiently close to the beam axis directions. The jets containing two and three particles including charged leptons, photons and pseudoscalar mesons are considered explicitly. Considering the pair production subprocesses we take into account both bremsstrahlung and double photon mechanisms. The obtained results are suitable for further numerical calculations…
At future $γγ$ colliders copious production of $t \bar{t}$ pairs is possible. This would allow a detailed investigation of the interactions involving the top quark. We propose some orrelations which are sensitive to $t \bar{t}$ final state interactions and we compute the QCD and standard model Higgs boson contributions to these correlations. QCD induced transverse polarization of top quarks is found to be sizeable and measurable at a high-energy $e^+e^-$ collider with an integrated luminosity of 10 $({\rm fb})^{-1}$ which is converted into a photon collider by backscattering of laser photons.
We present a comprehensive analysis on the MSSM Higgs sector CP violation at photon colliders including the chargino contributions as well as the contributions of other charged particles. The chargino loop contributions can be important for the would-be CP odd Higgs production at photon colliders. Polarization asymmetries are indispensable in determining the CP properties of neutral Higgs bosons.
We study the inclusive production of doubly heavy baryon $Ξ_{cc}$ at polarized photon collider. Our results show that proper choice of the initial beam polarizations may increase the production rate of $Ξ_{cc}$ approximately 10%.
In this report our main attention is focused on the problems which can be solved at Photon Colliders naturally but are hardly solved at LHC and e^+e^- Linear Collider: The New Physics - new particles, new interactions, supersymmetry, Dirac monopole, extra dimensions... SM and the case of a SM--like scenario - EWSB, Higgs bosons, anomalies in interactions of gauge bosons, QCD, Pomeron and odderon... By-product: Production of light Goldstone particles from region of e\toγconversion.
Recent progress in calculating O(alpha) electroweak corrections to W+W- pair production in photon-photon collisions is reviewed. The potential of the Photon Linear Collider to study anomalous W couplings is discussed.
The novel possibilities of probing the photon structure and high energy limit of QCD at photon colliders are summarised. We discuss the photon structure function $F_2^γ(x,Q^2)$, the gluon distribution in the photon and the spin dependent structure function $g_1^γ(x,Q^2)$ of the photon and emphasise advantages of the photon colliders for measuring these quantities. The possibility of probing the QCD pomeron and odderon in $γγ$ and $e γ$ collisions is also described.
Feasibility of a measurement of the partial decay width of the intermediate-mass Higgs boson into two photons at a photon-photon collider is studied by a simulation. The QCD radiative correction for quark pair background processes is taken into account for the realistic background estimation. It is found that the two-photon decay width can be measured with the statistical error of 7.6 % with about one year of experiment. The impact of the measurement of the two-photon decay width to look for the new physics beyond is demonstrated.
The use of the existing proton storage rings combined with electron linear accelerator as a ring-linac type electron-proton or photon-proton collider is investigated. The total CM-energy of Proton-ring and Electron-linac Collider (PRELC) is in the range of 1.0 TeV. The most important physical issues are listed and the most critical machine aspects of the PRELC are studied. It is shown that the luminosities in the range of $10^{31}$ to $10^{32}$ could be achieved. The PRELC could be used simultaneously with the $e^+e^-$-collider if the refocused electron beam could be used as the electron beam …
We present methods to measure the beam polarizations and the luminosity of $γγ$ colliders at TeV energy scale. The beam polarizations of a $γγ$ collider can easily be monitored by comparing the numbers of events of the processes $γγ$ $\rightarrow$ $\ell^+ \ell^-$ and $γγ$ $\rightarrow$ $W^+ W^-$, where $\ell$ means $e$ or $μ$. The luminosity of a $γγ$ collider is also measurable by the event rate of $W$ boson pair productions and the light lepton pair productions.
The ability of high energy lepton and photon colliders to probe the gauge couplings of the top-quark is summarized.
We investigate ττfusion to light h and heavy H and A Higgs bosons in the Minimal Supersymmetric Standard Model (MSSM) at a photon collider as a promising channel for measuring large values of tan(beta). For standard design parameters of a photon collider an error Δtan(beta) \sim 1, uniformly for tan(beta) \gsim 10, may be expected, improving on complementary measurements at the LHC and e+e- linear colliders.
The aim of this paper is twofold: to provide a rather detailed and self-contained introduction into the physics of the Disoriented Chiral Condensate (DCC) for the photon (and linear) collider community, and to indicate that such physics can be searched and studied at photon colliders. Some side tracks are also occasionally followed during the exposition, if they lead to interesting vistas. For gourmets, the Baked Alaska recipe is given in the appendix.
Isolated photons at hadron colliders are defined by permitting only a limited amount of hadronic energy inside a fixed-size cone around the candidate photon direction. This isolation criterion admits contributions from collinear photon radiation off QCD partons and from parton-to-photon fragmentation processes. We compute the NNLO QCD corrections to isolated photon and photon-plus-jet production, including these two contributions. Our newly derived results allow us to reproduce the isolation prescription used in the experimental measurements, performing detailed comparisons with data from the …
In this review we demonstrate physics potential of a photon linear collider by studying the neutral Higgs-boson sector of the MSSM in which interesting CP-violating Higgs mixing could arise via radiative corrections.
After a brief description of the basic principle of a photon collider, we summarize the physics potential of such a facility at high energies. Unique opportunities are provided in supersymmetric theories for the discovery of heavy scalar and pseudoscalar Higgs bosons as well as selectrons and e-sneutrinos.
In addition to being interesting in itself, the photon-photon interactions will be an inevitable background for the future electron-positron colliders. Thus to be able to quantify the potential of future electron-positron colliders it is important to have an accurate description of these collisions. Here we present our ongoing work to implement the photon-photon collisions in the Pythia 8 event generator. First we introduce photon PDFs in general and then discuss in more detail one particular set we have used in our studies. Then we will discuss how the parton-shower algorithm in Pythia 8 is m…
It is demonstrated that measurements of the spin asymmetry for di-jet production at future polarized colliders appear to be particularly suited for a first determination of the so far unmeasured parton densities of circularly polarized photons.
We examine the prospects for studying the diffractive production of high pt photons in the process gamma+gamma -> gamma+X at a future linear collider operating in both ee and gamma-gamma modes. The high luminosity associated with a linear collider make it the ideal place to measure this process.
We study the effect of heavy neutral Higgs bosons on the top pair production process at photon linear colliders.The interference patterns betwenn the resonant Higgs production amplitudes and the continuum QED amplitudes are examined. The patterns are sensitive to the phase of the photon-photon-Higgs vertex which is a good probe of new charged particles.
A high energy linear e^+e^- collider (LC) can also be used as a Photon Collider (PC), using Compton scattering of laser photons on the e^+/e^- beams. The leading order cross-section for the production of heavy quarks, e^+e^- -> e^+e^- Q(\bar{Q}) X, at high transverse momenta is calculated for both LC and PC modes. The sensitivity of this process to the parton distribution parametrizations of real photons, especially the gluon content, is tested for both modes.
By realizing the project of intensive $γ$ beams with large energy (necessary for Photon Colliders) an essential flux of light Goldstone particles (LGP - axions, arions, familons, majorons) can be generated. The probability of LGP production is calculated for different densities of laser photons in the conversion region (with absorption of one or several laser photons). The method for observation of LGP via its absorption in the matter is also presented.
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.
Heavy quark production is studied at the high energy linear e^+e^- collider (LC) TESLA both in its nominal and Photon Collider (PC) mode. Leading order cross-sections are calculated for the production of heavy quarks, e^+e^- -> e^+e^- Q\bar{Q}X, at high transverse momenta. The sensitivity of this process to the gluon content in the photon is studied.
A description and the use of an event-generator code for two-photon processes at e+e- colliders, TREPS, are presented. This program uses an equivalent photon approximation in which the virtuality of photons is taken into account. It is applicable to various processes by specifying a combination of final-state particles and the angular distributions among them. A comparison of the results with those from other programs is also given.
The CP properties of Higgs bosons can be probed through their s-channel resonance productions via photon-photon collisions by use of circularly and/or linearly polarized backscattered laser photons at a TeV-scale linear e^+ e^- collider. Exploiting this powerful tool, we investigate in detail the Higgs sector of the minimal supersymmetric Standard Model with explicit CP violation.
We study the prospects for probing the quark content of the photon using b tagging at high energy electron-photon colliders. We find that heavy quark tagging provides a sensitive and effective probe of the quark content of the photon. Using a 500 GeV $e^+e^-$\ NLC in electron-photon mode, the cross section for $eb_γ\rightarrow eb$\ can be measured to 10\% with b tagging. This is sufficient to differentiate between the various photon structure functions.
We show the usefulness of an $e^-γ$ collider with backscattered laser photons in unveiling the signatures of Gauge-Mediated Supersymmetry Breaking models, with a right selectron as the next LSP. We also show how the signal can be distinguished from the Standard Model background as well as from signals of minimal supersymmetry.
The theoretical and experimental aspects of particle production from the strong equivalent photon fluxes present at high energy hadron colliders are reviewed. The goal is to show how photons at hadron colliders can improve what we have learnt from experiments with lepton beams. Experiments during the last 5-10 years have shown the feasibility of studying photoproduction in proton-proton and heavy-ion collisions. The experimental and theoretical development has revealed new opportunities as well as challenges.
Two photons can annihilate into a neutral pion-like resonance via the anomaly coupling, just like $π^0γγ$ in QCD. In some strongly interacting electroweak symmetry breaking models, e.g., technicolor type models, there often exist neutral pion-like resonances. TeV photon colliders have a strong capability to discover such particles, because the standard model background in photon scattering goes through box diagrams and is therefore highly suppressed. In this study, we perform a signal-background comparison. We show that $e^+ e^-$ linear colliders running in $γγ$ mode can discover such neutral-…
We study top quark pair productions at a polarized photon collider from an e(+)e(-) linear collider (LC) in various improved technicolor model, namely, the one-family walking technicolor model, the top-color-assisted technicolor model, and the top-color-assisted multiscale technicolor model. Recent constraint on the top-pion mass from the precision data of R(b) is considered. It is shown that, considering only the statistical errors, a polarized photon collider from a 500 GeV LC with an integrated luminosity of 500 inverse fb is sufficient for distinguishing the three improved technicolor mode…
The physical program for the photon linear colliders (PLC) is discussed. We consider the problems in electroweak theory, hadron physics and QCD, new particles and interactions. We arrange this program for the main stages of PLC, which are the parts of an entire program for linear colliders. Some important unsolved problems are listed.
We study measurement of the CP property of the Higgs boson at a photon linear collider. One method where we take advantage of interference between Higgs-production and background amplitudes is proposed. A broad peak of the photon energy spectrum is helpful in observing the energy dependence of the interference effects. Numerical results for the process $γγ\to t \bar{t}$ are shown as an example.
We analyze the spin correlations of the top quark pairs produced at Photon Linear Colliders. We employ the circular polarized photon beams and general spin basis for the top quark pair. We consider general spin bases to find a strong spin correlation between produced top quark and anti-top quark. We show the cross-section in these bases and discuss the characteristics of results.
We report on the accuracy of the measurement of the two photon decay width of a Higgs boson with the mass of 120 GeV at the TESLA Photon Collider, assuming a $γγ$ integrated luminosity of 80 fb$^{-1}$ in the hard part of the spectrum. The QCD radiative corrections for the quark pair background processes are taken into account by a reweighting procedure. We found that the product $Γ(\rm H \to γγ) \times \rm BR (\rm H \to \rm b \bar{\rm b})$ can be measured with the statistical error of 1.8% in one year of run.
The feasibility of an experimental determination of the parton distributions of virtual photons at high energy $ep$ colliders is studied in the context of the DESY-HERA collider. Recently proposed parton densities of virtual photons are utilized to evaluate the appropriate production processes and their relevant kinematical regions. It is demonstrated that high $E_T$ jet production with $E_T\,\simeq 5-7\, {\rm{GeV}}$ and $b\bar{b}$ production can probe the parton distributions of virtual photons up to virtualities of a few ${\rm{GeV}}^2$. A useful leading order parametrization of our proposed …
$γγ\toγZ$ scattering at the Photon Linear Collider is considered. Explicit formulas for helicity amplitudes due to $W$ boson loops are presented. It is shown that the $Zγ$ pair production will be easily observable at PLC and separation of the $W$ loop contribution will be possible at $e^+e^-$ c.m. energy of 300~GeV or higher.
A Higgs boson within the mass range $M_H=140-190$ GeV can be discovered at a photon collider in the reaction $γγ\to WW$ (with real or virtual W) with the luminosity integral about 1 fb$^{-1}$. The reasonable resolution in the effective mass of the WW system is required.
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