The HERA-B Ring Imaging Cherenkov Counter

The HERA-B RICH uses a radiation path length of 2.8 m in C_4F_10 gas and a large 24 square meters spherical mirror for imaging Cherenkov rings. The photon detector consists of 2240 Hamamatsu multi-anode photomultipliers with about 27000 channels. A 2:1 reducing two-lens telescope in front of each PMT increases the sensitive area at the expense of increased pixel size, resulting in a contribution to the resolution which roughly matches that of dispersion. The counter was completed in January of 1999, and its performance has been steady and reliable over the years it has been in operation. The design performance of the RICH was fully reached: the average number of detected photons in the RICH for a beta=1 particle was found to be 33 with a single hit resolution of 0.7 mrad and 1 mrad in the fine and coarse granularity regions, respectively.Comment: 29 pages, 23 figure

Expression of Interest: A Muon to Electron Conversion Experiment at Fermilab

We are writing this letter to express our interest in pursuing an experiment at Fermilab to search for neutrinoless conversion of muons into electrons in the field of a nucleus, which is a lepton flavor-violating (LFV) reaction. The sensitivity goal of this experiment, improving on existing limits for this process by more than a factor of 10000, is very similar to that of previous experiments that have been proposed but never built. It would provide the most sensitive test of LFV, a unique and essential window on new physics unavailable at the high energy frontier. We present a conceptual scheme that would exploit the existing Accumulator and Debuncher rings to generate the required characteristics of the primary proton beam. The proposal requires only modest modifications to the accelerator complex after including those already planned for the NOvA experiment, with which this experiment would be fully compatible. The search for lepton flavor violation (LFV) has long played an important role in the evolution of our understanding of electroweak interactions. The neutrinoless conversion of a muon to an electron in the field of a nucleus is a particularly interesting example of an LFV process involving charged leptons. In the Standard Model, such conversions would take place via loop diagrams involving virtual neutrino mixing, at a rate far below the threshold of any currently conceivable experiment. Indeed, any detectable signal would be a definite indication, albeit indirect, of new dynamics at multi-TeV energy scales. Enhanced rate for this process is an almost universal feature of beyond the Standard Model physics, and the fact that such a process has not been observed has constrained or eliminated many models [1]. While it is widely believed that new physics will appear at LHC energies, the LHC is not well-equipped to study LFV directly. An often-quoted example is in the case of supersymmetry. The LHC will probe slepton masses, but it cannot compete with muon decay experiments in constraining the slepton mixing angles. Sensitive searches for rare or forbidden leptonic and semi-leptonic LFV processes, especially those involving charged leptons, are essential for the comprehensive characterization of new high energy physics. While there are several potential reactions that can be used to probe LFV, muon to electron conversion has the remarkable feature that it does not require the coincidence of two final-state particles. The spectacular signature is a single conversion electron of well-defined energy, separated from most of the sources of background. As a result, very high muon data rates can be handled and an unusually sensitive search for LFV becomes feasible. Indeed, at the level of sensitivity discussed below, a large class of supersymmetric models would predict 100's of conversion events. Additionally, compositeness and Z{prime} models would be probed at the multi-TeV scale in a manner complementary to direct LHC searches. Lepto-quarks would be probed at the 3000 TeV scale. Muon to electron conversion is therefore sensitive to many new physics scenarios at energy scales that cannot be probed by direct searches using other foreseeable accelerators

Inclusive V0V^0 Production Cross Sections from 920 GeV Fixed Target Proton-Nucleus Collisions

Inclusive differential cross sections $d\sigma_{pA}/dx_F$ and $d\sigma_{pA}/dp_t^2$ for the production of \kzeros, \lambdazero, and \antilambda particles are measured at HERA in proton-induced reactions on C, Al, Ti, and W targets. The incident beam energy is 920 GeV, corresponding to $\sqrt {s} = 41.6$ GeV in the proton-nucleon system. The ratios of differential cross sections \rklpa and \rllpa are measured to be $6.2\pm 0.5$ and $0.66\pm 0.07$, respectively, for \xf $\approx-0.06$. No significant dependence upon the target material is observed. Within errors, the slopes of the transverse momentum distributions $d\sigma_{pA}/dp_t^2$ also show no significant dependence upon the target material. The dependence of the extrapolated total cross sections $\sigma_{pA}$ on the atomic mass $A$ of the target material is discussed, and the deduced cross sections per nucleon $\sigma_{pN}$ are compared with results obtained at other energies.Comment: 17 pages, 7 figures, 5 table

First measurement of electron neutrino appearance in NOvA

We report results from the first search for νμ→νe transitions by the NOvA experiment. In an exposure equivalent to 2.74×1020 protons on target in the upgraded NuMI beam at Fermilab, we observe 6 events in the Far Detector, compared to a background expectation of 0.99±0.11(syst) events based on the Near Detector measurement. A secondary analysis observes 11 events with a background of 1.07±0.14(syst). The 3.3σ excess of events observed in the primary analysis disfavors 0.1π<δCP<0.5π in the inverted mass hierarchy at the 90% C.L

First measurement of muon-neutrino disappearance in NOvA

This paper reports the first measurement using the NOvA detectors of νμ disappearance in a νμ beam. The analysis uses a 14 kton-equivalent exposure of 2.74×1020 protons-on-target from the Fermilab NuMI beam. Assuming the normal neutrino mass hierarchy, we measure Δm232=(2.52+0.20−0.18)×10−3  eV2 and sin2θ23 in the range 0.38–0.65, both at the 68% confidence level, with two statistically degenerate best-fit points at sin2θ23=0.43 and 0.60. Results for the inverted mass hierarchy are also presented

The QCD transition temperature: results with physical masses in the continuum limit II.

We extend our previous study [Phys. Lett. B643 (2006) 46] of the cross-over temperatures (T_c) of QCD. We improve our zero temperature analysis by using physical quark masses and finer lattices. In addition to the kaon decay constant used for scale setting we determine four quantities (masses of the \Omega baryon, K^*(892) and \phi(1020) mesons and the pion decay constant) which are found to agree with experiment. This implies that --independently of which of these quantities is used to set the overall scale-- the same results are obtained within a few percent. At finite temperature we use finer lattices down to a <= 0.1 fm (N_t=12 and N_t=16 at one point). Our new results confirm completely our previous findings. We compare the results with those of the 'hotQCD' collaboration.Comment: 19 pages, 8 figures, 3 table

Dark matter search results from the PICO-60 CF3I bubble chamber

New data are reported from the operation of the PICO-60 dark matter detector, a bubble chamber filled with 36.8 kg of CF3I and located in the SNOLAB underground laboratory. PICO-60 is the largest bubble chamber to search for dark matter to date. With an analyzed exposure of 92.8 livedays, PICO-60 exhibits the same excellent background rejection observed in smaller bubble chambers. Alpha decays in PICO-60 exhibit frequency-dependent acoustic calorimetry, similar but not identical to that reported recently in a C3F8 bubble chamber. PICO-60 also observes a large population of unknown background events, exhibiting acoustic, spatial, and timing behaviors inconsistent with those expected from a dark matter signal. These behaviors allow for analysis cuts to remove all background events while retaining 48.2% of the exposure. Stringent limits on weakly interacting massive particles interacting via spin-dependent proton and spin-independent processes are set, and most interpretations of the DAMA/LIBRA modulation signal as dark matter interacting with iodine nuclei are ruled out.The PICO Collaboration would like to thank SNOLAB and its staff for providing an exceptional underground laboratory space and invaluable technical support. We acknowledge technical assistance from Fermilab's Computing, Particle Physics, and Accelerator Divisions and from A. Behnke at IUSB. We thank V. Gluscevic and S. McDermott for useful conversations and their assistance with the DMDD code package. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award No. DE-SC-0012161. Fermi National Accelerator Laboratory is operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359. Part of the research described in this paper was conducted under the Ultra Sensitive Nuclear Measurements Initiative at Pacific Northwest National Laboratory, a multiprogram national laboratory operated by Battelle for the U.S. Department of Energy. We acknowledge the National Science Foundation for their support including Grants No. PHY-1242637, No. PHY-0919526, and No. PHY-1205987. We acknowledge the support of the National Sciences and Engineering Research Council of Canada (NSERC) and the Canada Foundation for Innovation (CFI). We thank the Kavli Institute for Cosmological Physics at the University of Chicago. We were also supported by the Spanish Ministerio de Economia y Competitividad, Consolider MultiDark CSD2009-00064 Grant. We thank the Department of Atomic Energy (DAE), Government of India, under the project CAPP-II at SINP, Kolkata. We acknowledge the Czech Ministry of Education, Youth and Sports, Grant No. LM2011027.Amole, C.; Ardid Ramírez, M.; Asner, DM.; Baxter, D.; Behnke, E.; Bhattacharjee, P.; Borsodi, H.... (2016). Dark matter search results from the PICO-60 CF3I bubble chamber. Physical Review D. 93(5):1-14. https://doi.org/10.1103/PhysRevD.93.052014S114935Komatsu, E., Dunkley, J., Nolta, M. R., Bennett, C. L., Gold, B., Hinshaw, G., … Wright, E. L. (2009). FIVE-YEARWILKINSON MICROWAVE ANISOTROPY PROBEOBSERVATIONS: COSMOLOGICAL INTERPRETATION. The Astrophysical Journal Supplement Series, 180(2), 330-376. doi:10.1088/0067-0049/180/2/330Jungman, G., Kamionkowski, M., & Griest, K. (1996). Supersymmetric dark matter. Physics Reports, 267(5-6), 195-373. doi:10.1016/0370-1573(95)00058-5Bertone, G., Hooper, D., & Silk, J. (2005). Particle dark matter: evidence, candidates and constraints. Physics Reports, 405(5-6), 279-390. doi:10.1016/j.physrep.2004.08.031Feng, J. L. (2010). Dark Matter Candidates from Particle Physics and Methods of Detection. Annual Review of Astronomy and Astrophysics, 48(1), 495-545. doi:10.1146/annurev-astro-082708-101659Goodman, M. W., & Witten, E. (1985). Detectability of certain dark-matter candidates. Physical Review D, 31(12), 3059-3063. doi:10.1103/physrevd.31.3059Bolte, W. J., Collar, J. I., Crisler, M., Hall, J., Holmgren, D., Nakazawa, D., … Vieira, J. D. (2007). Development of bubble chambers with enhanced stability and sensitivity to low-energy nuclear recoils. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 577(3), 569-573. doi:10.1016/j.nima.2007.04.149Behnke, E., Collar, J. I., Cooper, P. S., Crum, K., Crisler, M., Hu, M., … Tschirhart, R. (2008). Spin-Dependent WIMP Limits from a Bubble Chamber. Science, 319(5865), 933-936. doi:10.1126/science.1149999Behnke, E., Behnke, J., Brice, S. J., Broemmelsiek, D., Collar, J. I., … Cooper, P. S. (2011). Improved Limits on Spin-Dependent WIMP-Proton Interactions from a Two LiterCF3IBubble Chamber. Physical Review Letters, 106(2). doi:10.1103/physrevlett.106.021303Behnke, E., Behnke, J., Brice, S. J., Broemmelsiek, D., Collar, J. I., … Conner, A. (2012). First dark matter search results from a 4-kgCF3Ibubble chamber operated in a deep underground site. Physical Review D, 86(5). doi:10.1103/physrevd.86.052001Archambault, S., Aubin, F., Auger, M., Behnke, E., Beltran, B., Clark, K., … Zacek, V. (2009). Dark matter spin-dependent limits for WIMP interactions on 19F by PICASSO. Physics Letters B, 682(2), 185-192. doi:10.1016/j.physletb.2009.11.019Archambault, S., Behnke, E., Bhattacharjee, P., Bhattacharya, S., Dai, X., Das, M., … Zacek, V. (2012). Constraints on low-mass WIMP interactions on 19F from PICASSO. Physics Letters B, 711(2), 153-161. doi:10.1016/j.physletb.2012.03.078Felizardo, M., Girard, T. A., Morlat, T., Fernandes, A. C., Ramos, A. R., Marques, J. G., … Marques, R. 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E., Barros, N., Beier, E. W., … Biller, S. D. (2009). Measurement of the cosmic ray and neutrino-induced muon flux at the Sudbury neutrino observatory. Physical Review D, 80(1). doi:10.1103/physrevd.80.012001Agostinelli, S., Allison, J., Amako, K., Apostolakis, J., Araujo, H., Arce, P., … Barrand, G. (2003). Geant4—a simulation toolkit. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 506(3), 250-303. doi:10.1016/s0168-9002(03)01368-8Allison, J., Amako, K., Apostolakis, J., Araujo, H., Arce Dubois, P., Asai, M., … Chytracek, R. (2006). Geant4 developments and applications. IEEE Transactions on Nuclear Science, 53(1), 270-278. doi:10.1109/tns.2006.869826Aubin, F., Auger, M., Genest, M.-H., Giroux, G., Gornea, R., Faust, R., … Storey, C. (2008). Discrimination of nuclear recoils from alpha particles with superheated liquids. New Journal of Physics, 10(10), 103017. doi:10.1088/1367-2630/10/10/103017Yellin, S. (2002). Finding an upper limit in the presence of an unknown background. Physical Review D, 66(3). doi:10.1103/physrevd.66.032005Lewin, J. D., & Smith, P. F. (1996). Review of mathematics, numerical factors, and corrections for dark matter experiments based on elastic nuclear recoil. Astroparticle Physics, 6(1), 87-112. doi:10.1016/s0927-6505(96)00047-3Fitzpatrick, A. L., & Zurek, K. M. (2010). Dark moments and the DAMA-CoGeNT puzzle. Physical Review D, 82(7). doi:10.1103/physrevd.82.075004Fitzpatrick, A. L., Haxton, W., Katz, E., Lubbers, N., & Xu, Y. (2013). The effective field theory of dark matter direct detection. Journal of Cosmology and Astroparticle Physics, 2013(02), 004-004. doi:10.1088/1475-7516/2013/02/004Anand, N., Fitzpatrick, A. L., & Haxton, W. C. (2014). Weakly interacting massive particle-nucleus elastic scattering response. Physical Review C, 89(6). doi:10.1103/physrevc.89.065501Gresham, M. I., & Zurek, K. M. (2014). 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Dark Matter Search Results from the PICO-2L C3F8 Bubble Chamber

New data are reported from the operation of a 2 liter C3F8 bubble chamber in the SNOLAB underground laboratory, with a total exposure of 211.5 kg days at four different energy thresholds below 10 keV. These data show that C3F8 provides excellent electron-recoil and alpha rejection capabilities at very low thresholds. The chamber exhibits an electron-recoil sensitivity of 98.2%. These data also include the first observation of a dependence of acoustic signal on alpha energy. Twelve single nuclear recoil event candidates were observed during the run. The candidate events exhibit timing characteristics that are not consistent with the hypothesis of a uniform time distribution, and no evidence for a dark matter signal is claimed. These data provide the most sensitive direct detection constraints on WIMP-proton spin-dependent scattering to date, with significant sensitivity at low WIMP masses for spin-independent WIMP-nucleon scattering.The PICO Collaboration would like to thank SNOLAB and its staff for providing an exceptional underground laboratory space and invaluable technical support. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under award DE-SC-0012161. Fermi National Accelerator Laboratory is operated by Fermi Research Alliance, LLC under Contract No. De-AC02-07CH11359. Part of the research described in this paper was conducted under the Ultra Sensitive Nuclear Measurements Initiative at Pacific Northwest National Laboratory, a multiprogram national laboratory operated by Battelle for the U.S. Department of Energy. We acknowledge the National Science Foundation for their support including Grants No. PHY-1242637, No. PHY-0919526, and No. PHY-1205987. We acknowledge the support of the National Sciences and Engineering Research Council of Canada (NSERC) and the Canada Foundation for Innovation (CFI). We also acknowledge support from the Kavli Institute for Cosmological Physics at the University of Chicago. We acknowledge the financial support of the Spanish Ministerio de Economia y Competitividad, Consolider MultiDark CSD2009-00064 Grant. We acknowledge support from the Department of Atomic Energy (DAE), Government of India, under the Center for AstroParticle Physics II project (CAPP-II) at Saha Insititute of Nuclear Physics (SINP), Kolkata. We acknowledge the Czech Ministry of Education, Youth and Sports, Grant No. LM2011027. We acknowledge technical assistance from Fermilab's Computing, Particle Physics, and Accelerator Divisions, and from A. 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