Large bulk matter search for fractional charge particles

Abstract

We have carried out the largest search for stable particles with fractional electric charge, based on an oil drop method that incorporates a horizontal electric field and upward air flow. No evidence for such particles was found, giving a 95% C.L. upper limit of $1.17\times 10^{-22}$ particles per nucleon on the abundance of fractional charge particles in silicone oil for $0.18 e \le |Q_{residual}| \le 0.82 e$. Since this is the first use of this new method we describe the advantages and limitations of the method.Comment: 11 pages, 9 figures, 3 table

Search for Millicharged Particles Using Optically Levitated Microspheres

“…The resulting limit on the abundance per nucleon, n χ , of particles with charge ±ǫe is shown in Fig. 4, and compared to previous limits from oil drop [5,18] and magnetic levitometer [14,16,17] experiments. The gray shaded region denotes the parameter space directly excluded by the present results assuming the residual on each microsphere could be due to a single millicharged particle.…”

“…Previous bulk matter searches using magnetic levitometers [14][15][16][17] or high-throughput Millikan oil drop techniques [5,[18][19][20] focused on searching for free quarks with ǫ = 1/3, and did not have sensitivity to single fractional charges with ǫ 0.1 e. In this work we present results from a search for particles with ǫ 10 −5 e in bulk matter using optically levitated microspheres in high vacuum [21]. At high vacuum, residual dissipation of the microsphere motion from gas collisions becomes small, and measuring the motion of the microsphere in three dimensions allows extremely sensitive force detection [21,22].…”

A Simple Model of Gauged Lepton and Baryon Charges

“…However, our proposal is different from the cases of the charged, next-to-lightest supersymmetric particles which can decay (Dimopoulos et al, 1997;Giudice and Rattazzi, 1999). If the stable scalar χ is produced at some collider or coming from cosmic rays, halo particles, or bulk matter (Perl, 2008;Perl et al, 2009;Ambrosio et al, 2000;Kim et al, 2007;Lee et al, 2002), it can easily escape from the detectors. Indeed, the general collider detectors cannot be used to find particles with an electric charge smaller than 1/3 due to the uncertainty in trace reconstruction (Perl, 2008;Perl et al, 2009).…”

“…The searches for its impinging on the earth due to the cosmic rays or halo particles have been sensitive only to the smallest charges of 1/5 (Perl et al, 2001;Ambrosio et al, 2000). The bulk matter and sea water searches (only with integer charges) (Smith and Bennett, 1979; and so forth, up to Chuzhoy and Kolb, 2009) have a similar sensitivity (Kim et al, 2007;Lee et al, 2002;Perl et al, 2000;. There are also searches for millicharge particles with charges smaller than 0.1, which are irrelevant (see, for a review, Perl, 2008).…”

Search for lightly ionizing particles using CDMS-II data and fabrication of CDMS detectors with improved homogeneity in properties

“…1σ error bars, in broken lines, are also shown, but they get hidden due to the enormity of ordinate scales. The 90% Confidence Level limits for LIP flux from MACRO (grey), LSD (maroon +) and Kamiokande (purple X) are also shown (based on data from [10] [209,222]. .…”