Experimental studies
Experimental studies
This area is tentatively covered by 11 working groups:
WG1: Electroweak physics at the Z-pole
WG2: Di-boson physics at the WW threshold and above
WG7: Rare decays and search for new physics
WG9: Offline software and computing
WG10: Online software and computing
WGs 5, 6, and 7 are merged with theoretical WGs 3, 4 and 5.
Details on each WG is provided below:
The main mandate of this group is to understand the precision with which TLEP could measure all electroweak observables, by accumulating the LEP1 statistics every 15 minutes. The dominant three sources of systematic uncertainty at LEP and SLC were (i) the accuracy of the beam energy measurement, for the determination of the Z mass and width; (ii) the accuracy of the integrated luminosity measurement, for the absolute determination of the peak cross section and the number of light neutrinos; and (iii) the accuracy of the longitudinal polarization measurement, for the determination of the left-right asymmetry ALR. Another limitation in the interpretation of the results is the knowledge of the electromagnetic and strong coupling constants at the Z scale. These aspects are to be addressed in the group, as well as the other sources of systematic uncertainties, together with possible solutions to overcome the related limitations, and the pertaining constraints on the relevant detectors.
Di-boson production at TLEP includes e+e−→W+W−, ZZ, Zγ or γγ processes. The large TLEP instantaneous luminosities above the WW threshold and up to √s = 350 GeV will deliver large samples of di-boson and even tri-boson events. For example, in a configuration with four interaction points, 25 million W pairs are expected at the WW threshold within a year, and 150 (30) million W pairs above at s√=240 (350) GeV in a period of five years. These large statistics enable the measurements of many electroweak parameters with unprecedented accuracies. Among these measurements are the mass and the width of the W boson, mW and ΓW, the tri-linear and quadri-linear gauge couplings, or the WWH coupling gW. This group is expected to outline the pertaining experimental strategy, and to evaluate the TLEP potential for all the measurements.
With an instantaneous luminosity of 5×1034cm−2s−1 in each of the four interaction points, TLEP would produce of the order of 400,000 Higgs bosons per year when running as a Higgs factory (√s≃240GeV) through the Higgs-strahlung process e+e−→HZ. When running at the tt¯ threshold (√s≃345GeV) with an instantaneous luminosity of 1.3×1034cm−2s−1, about 80,000 Higgs bosons would be produced per year, of which 15,000 through the WW fusion process. After a five-year data-taking period at each centre-of-mass energy, over two million HZ events and about 75,000 WW→H events will be collected. The primary aim of this group is to evaluate the Higgs coupling measurement accuracies as a function of the performance of the detector, so as to come up with educated suggestions/constraints to give to the Working Group "Detector Design". Another goal is to thoroughly estimate the precisions achievable with TLEP luminosities.
The physics programme of TLEP is completed with a five years run at the tt¯ threshold with an instantaneous luminosity of 1.3×1034cm−2s−1 at each interaction point, in a configuration with four interaction points. A scan of the threshold would therefore provide a sample of about one million top quark pairs, enabling the measurements of the top mass and width with unprecedented accuracies as well as a first measurement of the ttH coupling λt. The mandate of the group is to outline the pertaining experimental strategy, and to evaluate and summarize the TLEP potential.
This group will work jointly with Th/WG3, which will study in an integrated framework the information that TLEP could extract from top studies, b, c and τ physics, and rare decays. Therefore it will liaise closely with the experimental Working Groups 4 and 7. The huge samples of heavy flavours produced under clean conditions will provide unprecedented sensitivity in the search for new Physics beyond the CKM paradigm.
This group will work jointly with Th/WG4, which will develop QCD predictions both for their intrinsic interest, e.g., for jet and fragmentation studies, measuring αs and testing theoretical predictions for γγ physics, and in view of their importance for attaining the desired precision objectives in other TLEP studies. The work programme of this group will include both novel higher-order perturbative QCD calculations and a new generation of event simulations. Thus this group will liaise with the experimental Working Groups 1 to 5.
This group will work jointly with Th/WG5. With almost a trillion Z, 100 million W, 2 million Higgs bosons, and 2 million top quarks, search for rare decays is an important part of the scientific programme of TLEP. The mandate of the group is to evaluate the potential of TLEP in this respect, as well as that of the specific searches for rare or new physics (e.g., dark matter detection through ISR, searches for effects of heavy neutrinos, effects of possible new resonances, etc.). The complementarity with hadron colliders is to be reviewed by the group.
The specific experimental environment of TLEP (intense and flat beams, large focalization close to the interaction point, presence of an injector ring close to the collider ring, possibly large number of bunches...) may have subtle effects by superimposing a variety of backgrounds on top of each collision. These backgrounds may affect the precision of a number of measurements, from the integrated luminosity determination to the Higgs boson coupling measurements. A detailed investigation is performed, and a suite of software tools is proposed for their simulation. The deliverable of the group is a suite of software tools aimed at evaluating and simulating each of the backgrounds. A review of what has been done for the Linear Collider studies is in order.
Taking the linear collider developments and the LHC current facilities as examples, the group should address issues like Monte Carlo generators (standard model processes at all energies and new physics signals), detector simulations (parameterized and fast), integration of beam background simulations, common analysis framework or simulated event sample production. A specific review of the computing (CPU and disk space) needs for the actual experiment is in order, to cope with the expected 15 kHz of hadronic Z decays and 60 kHz of small angle Bhabha scattering.
The main objective of this group is to understand how to cope with 15 kHz of hadronic Z decays and 60 kHz of Bhabha, from the viewpoints of data acquisition, trigger, online reconstruction and calibration, and maybe online analysis (?) at the Z pole. Trigger conditions should also be established at all centre-of-mass energies. More basically, defining a clear programme of work for TLEP to have a robust online architecture in view of an efficient data taking is also part of the mandate of the group.
The objective of the working group is to propose hardware solutions that would match the constraints from the studies of the Working Groups "Electroweak Precision Measurements at the Z pole" and "H(126) Properties", in particular. Synergies with linear collider developments ought to be sought whenever appropriate. In general, the whole detector must be particle-flow friendly, i.e, with adequate calorimeter granularity and good hadron detection efficiency down to 1 GeV, large magnetic field, light tracker, and excellent muon efficiency.
