F. Schrempp - Academia.edu (original) (raw)

Papers by F. Schrempp

Nuclear Physics B, 1991

We investigate the experimental signatures of the recently proposed "geometrical" production of m... more We investigate the experimental signatures of the recently proposed "geometrical" production of many W, Z, Higgs and (primordial) fermions (n w = a~t = 30) with a relatively large cross section. We believe that such events, if they exist, stand a very good chance to be seen at the LHC (SSC) provided that the (parton) threshold energy for the onset of geometrical flavour production is below 11 (28) TeV.

We present a first status report on a broad and systematic study of possible manifestations of QC... more We present a first status report on a broad and systematic study of possible manifestations of QCD-instantons at HERA. Considerable motivation comes from the close analogy between instanton-induced B+L violation in electroweak processes and effects of QCD-instantons in deep inelastic scattering. We concentrate on the high multiplicity final state structure, reminiscent of an isotropically decaying “fireball”. A set of experimental isolation criteria is proposed. They serve to further enhance the striking event signature without significantly suppressing the expected rates.

arXiv: High Energy Physics - Phenomenology, 1996

We present a brief status report of our broad and systematic study of QCD-instantons at HERA.

The purpose of this report is an investigation of the potential of LEP II to unravel possible sub... more The purpose of this report is an investigation of the potential of LEP II to unravel possible substructure of leptons, quarks, and perhaps, of the W )pluse))minus) and Z vector bosons. The main aspects are inclusion of initial-state polarization as an analysing tool; a thorough investigation of e/sup +/e⁻ yield W/sup +/W⁻, more precisely of compositeness-motivated deviations from the Standard

Phys Lett B, 1991

We examine the potential of a future 500 GeV linear e + e − collider (NLC) to probe the “minimal”... more We examine the potential of a future 500 GeV linear e + e − collider (NLC) to probe the “minimal” set ( γ , λ γ ) of anomalous WWγ and WWγγ couplings via the (sub) processes γ→W + W − , e − γ→W − v and e + e − →W + W − , for comparison. Photon beams both from ...

Eprint Arxiv Hep Ph 9805492, May 28, 1998

A "fiducial" kinematical region for our calculations of instanton (I)-induced processes at HERA w... more A "fiducial" kinematical region for our calculations of instanton (I)-induced processes at HERA within I-perturbation theory is extracted from recent lattice simulations of QCD. Moreover, we present the finalized I-induced cross-sections exhibiting a strongly reduced residual dependence on the renormalization scale.

Eprint Arxiv Hep Ph 0507160, Jul 1, 2005

A first part of this review is devoted to a summary of our extensive studies of the discovery pot... more A first part of this review is devoted to a summary of our extensive studies of the discovery potential for instanton (I)-induced, deep-inelastic processes at HERA. Included are some key issues about I-perturbation theory, an exploitation of crucial lattice constraints and a status report about the recent I-search results by the HERA collaborations H1 and ZEUS in relation to our predictions. Next follows a brief outline of an ongoing project concerning a broad exploration of the discovery potential for hard instanton processes at the LHC. I then turn to an overview of our work on high-energy processes, involving larger-sized instantons. I shall mainly focus on the phenomenon of saturation at small Bjorken-x from an instanton perspective. In such a framework, the saturation scale is associated with the conspicuous average instanton size, ρ ∼ 0.5 fm, as known from lattice simulations. A further main result is the intriguing identification of the "Colour Glass Condensate" with the QCD sphaleron state.

Instantonen stellen einen wesentlichen nichtperturbativen Aspekt der Theorie der starken Wechselw... more Instantonen stellen einen wesentlichen nichtperturbativen Aspekt der Theorie der starken Wechselwirkung dar. Dies macht es interessant, die Bedeutung von Instantonen in der tiefinelastischen Streuung bei kleinem Bjorken-x Bj und abnehmendem Q 2 zu untersuchen. Insbesondere wird gezeigt, daß Instantonen aufgrund ihrer intrinsischen, mit der Ausdehnung ρ verknüpften Skala zum vieldiskutierten Phänomen der Saturation bei kleinem Bjorken-x Bj beitragen.

We report on the interesting possibility of instanton-driven gluon saturation in lepton-nucleon s... more We report on the interesting possibility of instanton-driven gluon saturation in lepton-nucleon scattering at small Bjorken-x. The explicitly known instanton gauge field serves as a concrete realization of an underlying non-perturbative saturation mechanism associated with strong classical fields. The conspicuous, intrinsic instanton size scale known from lattice simulations, turns out to determine the saturation scale. The "colour glass condensate" can be identified in our approach with the QCD-sphaleron state, dominating instanton-induced processes in the softer regime.

Strong and Electroweak Matter 2002, 2003

We briefly report on the contribution of QCD-instantons to the phenomenon of saturation in deep-i... more We briefly report on the contribution of QCD-instantons to the phenomenon of saturation in deep-inelastic scattering (DIS) at small Bjorken-x. The explicitly known instanton gauge field serves as a concrete realization of an underlying nonperturbative saturation mechanism associated with strong classical fields. Two independent strategies were pursued, with consistent results: On the one hand, an approach starting from instanton-perturbation theory was considered and on the other hand, the scattering of a Wilson loop in an instanton gauge field background. In both cases, the conspicuous, intrinsic instanton size scale ρ ≈ 0.5 fm, as known from the lattice, turns out to determine the saturation scale.

Physics Letters B, 1982

A physically unique and simple solution of 't Hooft's anomaly matching equations in composite mod... more A physically unique and simple solution of 't Hooft's anomaly matching equations in composite models of the type SU(3)MC × SU(N) L X SU(N) R is found for N = 6, if an additional selection criterion for composite "ground states" is introduced.

We present a status report of our systematic theoretical and phenomenological study of QCD-instan... more We present a status report of our systematic theoretical and phenomenological study of QCD-instanton induced processes in deep-inelastic scattering. We show that this regime plays a distinguished rôle for studying manifestations of QCD-instantons, since the typical hard momentum scale Q provides a dynamical infrared cutoff for the instanton size ρ < ∼ O(1/Q). For deep-inelastic scattering at HERA, we present a preliminary theoretical estimate of the total instanton-induced cross-section (subject to appropriate kinematical cuts). It is surprisingly large, in the O(1 − 100) pb range, albeit still uncertain. We report on our investigation of the discovery potential for instanton-induced events at HERA by means of a Monte Carlo event generator. It is based on a detailed study of the characteristic signatures of the final state, like a large total transverse energy, E T = O(20) GeV, a large multiplicity, n = O(25), and a flavour-democratic production of hadrons. A combination of event shape information with searches of K 0 mesons, muons, and multiplicity cuts might help to discriminate further the QCD-instanton induced processes from the standard perturbative QCD background.

The present status of our ongoing systematic study of the discovery potential of QCD-instanton in... more The present status of our ongoing systematic study of the discovery potential of QCD-instanton induced events in deep-inelastic scattering at HERA is briefly reviewed. We emphasize our recent progress in predicting the cross-sections of instanton-induced processes. Our finalized predictions include a dramatic improvement of the residual renormalization-scale dependencies and the specification of a "fiducial" kinematical region in the relevant Bjorken variables extracted from recent lattice simulations. Published upper limits on instantoninduced cross-sections based on single observables in the final state such as the flow of strange particles and the multiplicity distribution of charged particles are already of the order of our estimate. Thus, a decisive search for instanton-induced events in deep-inelastic scattering at HERA, based on a multi-observable analysis, seems feasible.

Nuclear Physics B, 1991

We investigate the experimental signatures of the recently proposed "geometrical" production of m... more We investigate the experimental signatures of the recently proposed "geometrical" production of many W, Z, Higgs and (primordial) fermions (n w = a~t = 30) with a relatively large cross section. We believe that such events, if they exist, stand a very good chance to be seen at the LHC (SSC) provided that the (parton) threshold energy for the onset of geometrical flavour production is below 11 (28) TeV.

We present a first status report on a broad and systematic study of possible manifestations of QC... more We present a first status report on a broad and systematic study of possible manifestations of QCD-instantons at HERA. Considerable motivation comes from the close analogy between instanton-induced B+L violation in electroweak processes and effects of QCD-instantons in deep inelastic scattering. We concentrate on the high multiplicity final state structure, reminiscent of an isotropically decaying “fireball”. A set of experimental isolation criteria is proposed. They serve to further enhance the striking event signature without significantly suppressing the expected rates.

arXiv: High Energy Physics - Phenomenology, 1996

We present a brief status report of our broad and systematic study of QCD-instantons at HERA.

The purpose of this report is an investigation of the potential of LEP II to unravel possible sub... more The purpose of this report is an investigation of the potential of LEP II to unravel possible substructure of leptons, quarks, and perhaps, of the W )pluse))minus) and Z vector bosons. The main aspects are inclusion of initial-state polarization as an analysing tool; a thorough investigation of e/sup +/e⁻ yield W/sup +/W⁻, more precisely of compositeness-motivated deviations from the Standard

Phys Lett B, 1991

We examine the potential of a future 500 GeV linear e + e − collider (NLC) to probe the “minimal”... more We examine the potential of a future 500 GeV linear e + e − collider (NLC) to probe the “minimal” set ( γ , λ γ ) of anomalous WWγ and WWγγ couplings via the (sub) processes γ→W + W − , e − γ→W − v and e + e − →W + W − , for comparison. Photon beams both from ...

Eprint Arxiv Hep Ph 9805492, May 28, 1998

A "fiducial" kinematical region for our calculations of instanton (I)-induced processes at HERA w... more A "fiducial" kinematical region for our calculations of instanton (I)-induced processes at HERA within I-perturbation theory is extracted from recent lattice simulations of QCD. Moreover, we present the finalized I-induced cross-sections exhibiting a strongly reduced residual dependence on the renormalization scale.

Eprint Arxiv Hep Ph 0507160, Jul 1, 2005

A first part of this review is devoted to a summary of our extensive studies of the discovery pot... more A first part of this review is devoted to a summary of our extensive studies of the discovery potential for instanton (I)-induced, deep-inelastic processes at HERA. Included are some key issues about I-perturbation theory, an exploitation of crucial lattice constraints and a status report about the recent I-search results by the HERA collaborations H1 and ZEUS in relation to our predictions. Next follows a brief outline of an ongoing project concerning a broad exploration of the discovery potential for hard instanton processes at the LHC. I then turn to an overview of our work on high-energy processes, involving larger-sized instantons. I shall mainly focus on the phenomenon of saturation at small Bjorken-x from an instanton perspective. In such a framework, the saturation scale is associated with the conspicuous average instanton size, ρ ∼ 0.5 fm, as known from lattice simulations. A further main result is the intriguing identification of the "Colour Glass Condensate" with the QCD sphaleron state.

Instantonen stellen einen wesentlichen nichtperturbativen Aspekt der Theorie der starken Wechselw... more Instantonen stellen einen wesentlichen nichtperturbativen Aspekt der Theorie der starken Wechselwirkung dar. Dies macht es interessant, die Bedeutung von Instantonen in der tiefinelastischen Streuung bei kleinem Bjorken-x Bj und abnehmendem Q 2 zu untersuchen. Insbesondere wird gezeigt, daß Instantonen aufgrund ihrer intrinsischen, mit der Ausdehnung ρ verknüpften Skala zum vieldiskutierten Phänomen der Saturation bei kleinem Bjorken-x Bj beitragen.

We report on the interesting possibility of instanton-driven gluon saturation in lepton-nucleon s... more We report on the interesting possibility of instanton-driven gluon saturation in lepton-nucleon scattering at small Bjorken-x. The explicitly known instanton gauge field serves as a concrete realization of an underlying non-perturbative saturation mechanism associated with strong classical fields. The conspicuous, intrinsic instanton size scale known from lattice simulations, turns out to determine the saturation scale. The "colour glass condensate" can be identified in our approach with the QCD-sphaleron state, dominating instanton-induced processes in the softer regime.

Strong and Electroweak Matter 2002, 2003

We briefly report on the contribution of QCD-instantons to the phenomenon of saturation in deep-i... more We briefly report on the contribution of QCD-instantons to the phenomenon of saturation in deep-inelastic scattering (DIS) at small Bjorken-x. The explicitly known instanton gauge field serves as a concrete realization of an underlying nonperturbative saturation mechanism associated with strong classical fields. Two independent strategies were pursued, with consistent results: On the one hand, an approach starting from instanton-perturbation theory was considered and on the other hand, the scattering of a Wilson loop in an instanton gauge field background. In both cases, the conspicuous, intrinsic instanton size scale ρ ≈ 0.5 fm, as known from the lattice, turns out to determine the saturation scale.

Physics Letters B, 1982

A physically unique and simple solution of 't Hooft's anomaly matching equations in composite mod... more A physically unique and simple solution of 't Hooft's anomaly matching equations in composite models of the type SU(3)MC × SU(N) L X SU(N) R is found for N = 6, if an additional selection criterion for composite "ground states" is introduced.

We present a status report of our systematic theoretical and phenomenological study of QCD-instan... more We present a status report of our systematic theoretical and phenomenological study of QCD-instanton induced processes in deep-inelastic scattering. We show that this regime plays a distinguished rôle for studying manifestations of QCD-instantons, since the typical hard momentum scale Q provides a dynamical infrared cutoff for the instanton size ρ < ∼ O(1/Q). For deep-inelastic scattering at HERA, we present a preliminary theoretical estimate of the total instanton-induced cross-section (subject to appropriate kinematical cuts). It is surprisingly large, in the O(1 − 100) pb range, albeit still uncertain. We report on our investigation of the discovery potential for instanton-induced events at HERA by means of a Monte Carlo event generator. It is based on a detailed study of the characteristic signatures of the final state, like a large total transverse energy, E T = O(20) GeV, a large multiplicity, n = O(25), and a flavour-democratic production of hadrons. A combination of event shape information with searches of K 0 mesons, muons, and multiplicity cuts might help to discriminate further the QCD-instanton induced processes from the standard perturbative QCD background.

The present status of our ongoing systematic study of the discovery potential of QCD-instanton in... more The present status of our ongoing systematic study of the discovery potential of QCD-instanton induced events in deep-inelastic scattering at HERA is briefly reviewed. We emphasize our recent progress in predicting the cross-sections of instanton-induced processes. Our finalized predictions include a dramatic improvement of the residual renormalization-scale dependencies and the specification of a "fiducial" kinematical region in the relevant Bjorken variables extracted from recent lattice simulations. Published upper limits on instantoninduced cross-sections based on single observables in the final state such as the flow of strange particles and the multiplicity distribution of charged particles are already of the order of our estimate. Thus, a decisive search for instanton-induced events in deep-inelastic scattering at HERA, based on a multi-observable analysis, seems feasible.