Mass determination method for the left and right selectron above production threshold

Abstract

The determination of the masses of supersymmetric particles, such as the selectron, for energies above threshold using the energy end-point method is subject to signal deconvolution difficulties and to standard model and supersymmetry backgrounds. The important features of ẽ R,L Ϯ production are used to design an experimentally robust method, with good resolution, both for determining the ẽ R,L and the 1 0 masses and for suppressing backgrounds. Additional features, such as the determination of the relative leptonic branching ratios of the selectron are present in the method. The determination of supersymmetric particle masses using the energy end-point method ͓1͔ is well known. The measurement of selectron masses is subject to two experimental difficulties: on the one hand, the energy distribution of the visible particles in the event is an overlap of 4 ''box like'' distributions due to the production channels ẽϪ and, on the other, the supersymmetry ͑SUSY͒ signal is masked by very large standard model ͑SM͒ backgrounds, such as W ϩ W Ϫ and ␥*␥*. The consequences are, for the former, the difficulty of resolving overlapping ''box'' edges in the lower energy region making it hard to determine which edge is due to which SUSY particle decay, while, for the latter, the masking of the SUSY signal by large SM backgrounds.Many other studies ͓2-6͔ of the determination of supersymmetric masses via the energy spectrum of the observed particles have been carried out showing the usefulness of the technique and the levels of accuracy possible. The complications in the selectron spectrum are being solved here.We realized that the difference of the observed positron and electron ͑from the ẽ L,R decay͒ energy distributions enhanced by the difference in cross sections with incident electron polarization ͑possible only with a linear collider͒ can solve these problems and provide a method by which we can determine the masses unambiguously with good resolution. In addition it offers new features, builtin redundancy, and the determination of the partial leptonic branching ratios to the channels 1 Ϯ e and 1 0 e. Information about the 1 Ϯ and 1 Ϯ masses may, in principle, also be determined. The e ϩ , e Ϫ energy distributions difference is given bywhere, for instance, LR is the production cross section for ẽ L ϩ ẽ R Ϫ , while RЈ(E) and LЈ(E) are the appropriate energy box distributions ͑for the incident electron right-handed and left-handed polarization͒ each normalized to unity. The method presented here removes the contribution to the energy spectrum from the reactions producing ẽ R ϩ ẽ R Ϫ and ẽ L ϩ ẽ L Ϫ , which solves the mass measurement difficulty and reduces the mass errors.Asymmetric boosts are present when ẽ L Ϯ and ẽ R Ϯ are produced in the same reaction. The values of the boosts being, in this case,The energies of the electron and positron which are the particles visible in the event are related to the decay c.m. energy. Since m e ӶM L,R we obtain the lower and higher bounds of the electron or positron energy distribution in ...

Supersymmetry and the Linear Collider

“…Doing so, one finds that mμ R can be measured to within 0.4 GeV from kinematic endpoints, assuming an integrated luminosity of 160 fb −1 for this case. Of course, the same measurement can be done for selectrons, and the precision of the mass measurement is of the same order [59]. This provides an immediate and stringent test of scalar mass relations, such as the universality of scalar masses at the GUT scale discussed in Sec.…”

Undulator-Based Production of Polarized Positrons, A Proposal for the 50-GeV Beam in the FFTB

“…For many SUSY analyzes other SUSY processes are the most important background. Positron polarization can again be used to suppress the undesired process, as illustrated for selectron production in [16].…”

“…On reversing the sign of the magnetization of the absorber, an asymmetry δ is measured in the rate of transmitted photons, which is the product of the photon polarization P γ (and the polarization P e − of the electrons in the iron) and the analyzing power A γ of eq. (16).…”

Run Scenarios for the Linear Collider

“…The e R and e L end point studies are particularly rich, with distinct upper and lower edges coming from the distinct e R and e L decays to χ A new method to facilitate these analyses by taking differences between distributions with opposite beam polarizations, and between emitted positron and electron distributions was developed in this workshop [6].…”

“…The e R and e L are mixed in the e + e − / E final states, but Ref. [6] shows that they can be disentangled. Table VII shows some of the final states that are dominated by specific sparticle production processes.…”