Upper Limits on Sparticle Masses from g-2 and the Possibility for Discovery of SUSY at Colliders and in Dark Matter Searches


We analyze the implications of the new physics effect seen in the g-2 Brookhaven measurement and show that if the effect arises entirely from SUSY, then the sign of the Higgs mixing parameter μ is determined to be positive in the standard sign convention. Further, analyses within mSUGRA show that the BNL result leads to upper limits on chargino and neutralino masses of mW̃1 ≤ 600 GeV and mχ̃0 1 ≤ 300GeV and also leads to m 1 2 ≤ 750 GeV and m0 ≤ 1.1 TeV for tanβ ≤ 30. Our analysis strongly suggests that supersymmetry via production of sparticles must be found at the LHC, with also good prospects for its discovery at the Tevatron in Permanent address 1 some channels. Further, μ > 0 is favorable for the discovery of supersymmetric cold dark matter. The BNL g-2 experiment has made a precise determination of aμ[1]. The new measurement is in good agreement with the previous determinations but the combined error is now reduced by a factor of about 3. Remarkably the experiment finds a 2.6 sigma difference between the experiment and the Standard Model result[2] signaling the onset of new physics[1], i.e., a μ − a SM μ = 43(16)× 10 −10 (1) where aμ = (gμ−2)/2. It has been known for some time that aμ is sensitive to new physics such as SUSY[3, 4, 5]. Specifically, estimates of the correction in the well motivated SUGRA model showed in 1983-1984 that the supersymmetric correction to aμ can be as large or larger[5] than the Standard Model electro-weak correction[6, 2]. The more recent analyses[7, 8, 9] support the previous conclusions[5] that the supersymmetric electroweak effects can be large. Further, it is known that large CP effects can be consistent with the electron and the neutron edm constraints[10] and analyses show that the CP violations can generate large corrections to aμ[11]. A variety of other effects such as arising from extra dimensions, anomalous W-couplings etc have also been examined (for a review see Ref.[12]). In the following we analyze the implications of the new result from Brookhaven on sparticle masses. First, we show that the Brookhaven experiment determines the sign of the Higgs mixing parameter μ. We then analyze the limits on the sparticle spectrum by using the constraint of Eq.(1), combining the error in eq.(1) with the hadronic error of σSM = 6.7 × 10 [13], taking a 2 sigma error corridor and 2 attributing the entire difference between theory and experiment to supersymmetry, which gives 10.6 × 10 < a μ < 76.2 × 10 , where a μ = a exp μ − a SM μ . For the purpose of definiteness we shall give an analysis of the constraint mostly within the framework of mSUGRA[14]. However, for comparison we also discuss the results within the minimal anomaly mediated supersymmetry breaking (AMSB) scenario following the analysis of Ref.[9]. At low energy mSUGRA can be parameterized bym0, m 1 2 , A0, tanβ, sign(μ) where m0 is the universal scalar mass, m 1 2 is the universal gaugino mass, A0 is the universal trilinear coupling at the GUT scale and tanβ =< H2 > / < H1 > where < H2 > gives mass to the up quark and < H1 > gives mass to the down quark and the lepton, and μ is the Higgs mixing parameter which appears in the superpotential in the form W (2) = μH1H2 (Our sign convention on μ is that of Ref.[15]). The supersymmetric contributions a μ at the one loop level consists of the chargino-sneutrino exchange and of the neutralino-smuon exchange so that a μ = a W̃ μ + a Ñ μ . However, typically it is the chargino-sneutrino exchange contribution aμ that dominates. It was noted in two previous papers several years ago (see Ref.[7] and Chattopadhyay and Nath (CN)in Ref[8]) that the sign of a μ is correlated with the sign of μ. It was shown by CN in Ref.[8] that this correlation arises because of the signature carried by the contribution of the light chargino exchange term in the chiral left and the chiral right interference term in the chargino exchange contribution. It was found that over most of the parameter space one has a μ > 0 for μ > 0 and a SUSY μ < 0 and for μ < 0, except when tan β is very close to 1. Since the data from the BNL experiment indicates

Cite this paper

@inproceedings{Chattopadhyay2001UpperLO, title={Upper Limits on Sparticle Masses from g-2 and the Possibility for Discovery of SUSY at Colliders and in Dark Matter Searches}, author={Utpal Chattopadhyay and Pran Nath}, year={2001} }