ATLAS Collaboration(Abat, E. et al), Castillo Gimenez, V., Ferrer, A., Gonzalez, V., Higon-Rodriguez, E., Mitsou, V. A., et al. (2010). Study of energy response and resolution of the ATLAS barrel calorimeter to hadrons of energies from 20 to 350 GeV. Nucl. Instrum. Methods Phys. Res. A, 621(1-3), 134–150.
Abstract: A fully instrumented slice of the ATLAS detector was exposed to test beams from the SPS (Super Proton Synchrotron) at CERN in 2004. In this paper, the results of the measurements of the response of the barrel calorimeter to hadrons with energies in the range 20-350 GeV and beam impact points and angles corresponding to pseudo-rapidity values in the range 0.2-0.65 are reported. The results are compared to the predictions of a simulation program using the Geant 4 toolkit.
|
CDF Collaboration(Aaltonen, T. et al), & Cabrera, S. (2010). Search for the Production of Scalar Bottom Quarks in p(p)over-bar Collisions at root s=1.96 TeV. Phys. Rev. Lett., 105(8), 081802–7pp.
Abstract: We report on a search for direct scalar bottom quark (sbottom) pair production in p (p) over bar collisions at root s = 1.96 TeV, in events with large missing transverse energy and two jets of hadrons in the final state, where at least one of the jets is required to be identified as originating from a b quark. The study uses a collider detector at Fermilab Run II data sample corresponding to 2.65 fb(-1) of integrated luminosity. The data are in agreement with the standard model. In an R-parity conserving minimal supersymmetric scenario, and assuming that the sbottom decays exclusively into a bottom quark and a neutralino, 95% confidence-level upper limits on the sbottom pair production cross section of 0.1 pb are obtained. For neutralino masses below 70 GeV/c(2), sbottom masses up to 230 GeV/c(2) are excluded at 95% confidence level.
|
ATLAS Collaboration(Aad, G. et al), Amoros, G., Cabrera Urban, S., Castillo Gimenez, V., Costa, M. J., Escobar, C., et al. (2011). Search for massive long-lived highly ionising particles with the ATLAS detector at the LHC. Phys. Lett. B, 698(5), 353–370.
Abstract: A search is made for massive highly ionising particles with lifetimes in excess of 100 ns, with the ATLAS experiment at the Large Hadron Collider, using 3.1 pb(-1) of pp collision data taken at root s = 7 TeV. The signature of energy loss in the ATLAS inner detector and electromagnetic calorimeter is used. No such particles are found and limits on the production cross section for electric charges 6e <= vertical bar q vertical bar <= 17e and masses 200 GeV <= m <= 1000 GeV are set in the range 1-12 pb for different hypotheses on the production mechanism.
|
Agarwalla, S. K., Huber, P., Tang, J. A., & Winter, W. (2011). Optimization of the Neutrino Factory, revisited. J. High Energy Phys., 01(1), 120–45pp.
Abstract: We perform the baseline and energy optimization of the Neutrino Factory including the latest simulation results on the magnetized iron detector (MIND). We also consider the impact of tau decays, generated by v(mu) -> v(tau) or v(e) -> v(tau) appearance, on the mass hierarchy, CP violation, and theta(13) discovery reaches, which we find to be negligible for the considered detector. For the baseline-energy optimization for small sin(2) 2 theta(13), we qualitatively recover the results with earlier simulations of the MIND detector. We find optimal baselines of about 2 500km to 5 000km for the CP violation measurement, where now values of E-mu as low as about 12 GeV may be possible. However, for large sin(2) 2 theta(13), we demonstrate that the lower threshold and the backgrounds reconstructed at lower energies allow in fact for muon energies as low as 5 GeV at considerably shorter baselines, such as FNAL-Homestake. This implies that with the latest MIND analysis, low-and high-energy versions of the Neutrino Factory are just two different versions of the same experiment optimized for different parts of the parameter space. Apart from a green-field study of the updated detector performance, we discuss specific implementations for the two-baseline Neutrino Factory, where the considered detector sites are taken to be currently discussed underground laboratories. We find that reasonable setups can be found for the Neutrino Factory source in Asia, Europe, and North America, and that a triangular-shaped storage ring is possible in all cases based on geometrical arguments only.
|
Jido, D., Oset, E., & Sekihara, T. (2011). Kaon-induced Lambda(1405) production on a deuteron target at DAFNE. Eur. Phys. J. A, 47(3), 42–7pp.
Abstract: The K-- induced production of.(1405) in the K(-)d -> pi Sigma n reaction is investigated having in mind the conditions of the DAFNE facility at Frascati where kaons are obtained from the decay of slow-moving phi mesons. We find that the K(-)d -> Lambda(1405)n process favors the production of Lambda(1405) initiated by the K(-)p channel, which gives largest weight to the higher mass Lambda(1405) appearing at 1420MeV in chiral theories. We find that the fastest kaons from the decay of the phi are well suited to see this resonance, particularly if one selects forward going neutrons in the center of mass, which reduce the contribution of single scattering and make the double scattering dominate where the signal of the resonance appears clearer.
|
Li, X. Q., Su, F., & Yang, Y. D. (2011). Determination of the strong coupling gB*B pi from semileptonic B -> pi l nu decay. Phys. Rev. D, 83(5), 054019–8pp.
Abstract: According to heavy-meson chiral perturbation theory, the vector form factor f+(q(2)) of exclusive semileptonic decay B -> pi l nu is closely related, at least in the soft-pion region ( i.e., q(2) similar to (m(B) – m(pi))(2)), to the strong coupling g(B*B pi) or the normalized coupling (g)over-cap. Combining the precisely measured q2 spectrum of B -> pi l nu decay by the BABAR and Belle collaborations with several parametrizations of the form factor f +(q(2)), we can extract these couplings from the residue of the form factor at the B* pole, which relies on an extrapolation of the form factor from the semileptonic region to the unphysical point q(2) = m(B*)(2). Comparing the extracted values with the other experimental and theoretical estimates, we can test these various form-factor parametrizations, which differ from each other by the amount of physical information embedded in. It is found that the extracted values based on the Becirevic-Kaidalov, Ball-Zwicky and Bourrely-Caprini-Lellouch parametrizations are consistent with each other and roughly in agreement with the other theoretical and lattice estimates, while the Boyd-Grinstein-Lebed ansatz, featured by a spurious, unwanted pole at the threshold of the cut, gives a neatly larger value.
|
Esteves, J. N., Joaquim, F. R., Joshipura, A. S., Romao, J. C., Tortola, M., & Valle, J. W. F. (2010). A(4)-based neutrino masses with Majoron decaying dark matter. Phys. Rev. D, 82(7), 073008–8pp.
Abstract: We propose an A(4) flavor-symmetric SU(3) circle times SU(2) circle times U(1) seesaw model where lepton number is broken spontaneously. A consistent two-zero texture pattern of neutrino masses and mixing emerges from the interplay of type-I and type-II seesaw contributions, with important phenomenological predictions. We show that, if the Majoron becomes massive, such seesaw scenario provides a viable candidate for decaying dark matter, consistent with cosmic microwave background lifetime constraints that follow from current WMAP observations. We also calculate the subleading one-loop-induced decay into photons which leads to a monoenergetic emission line that may be observed in future x-ray missions such as Xenia.
|
CDF Collaboration(Aaltonen, T. et al), & Cabrera, S. (2010). Studying the underlying event in Drell-Yan and high transverse momentum jet production at the Tevatron. Phys. Rev. D, 82(3), 034001–21pp.
Abstract: We study the underlying event in proton-antiproton collisions by examining the behavior of charged particles produced in association with a large transverse momentum jet (similar to 2: 2 fb(-1)) or with a Drell-Yan lepton pair (similar to 2.7 fb(-1)) in the Z-boson mass region [70 < M(pair) < 110 GeV/c(2)] as measured by CDF at 1.96 TeV center-of-mass energy. We use the direction of the lepton pair or the leading jet in each event to define regions of eta-phi space that are sensitive to the modeling of the underlying event. The data are corrected to the particle level to remove detector effects and are then compared with several QCD Monte Carlo models.
|
Roszkowski, L., Ruiz de Austri, R., & Trotta, R. (2010). Efficient reconstruction of constrained MSSM parameters from LHC data: A case study. Phys. Rev. D, 82(5), 055003–12pp.
Abstract: We present an efficient method of reconstructing the parameters of the constrained MSSM from assumed future LHC data, applied both on their own right and in combination with the cosmological determination of the relic dark matter abundance. Focusing on the ATLAS SU3 benchmark point, we demonstrate that our simple Gaussian approximation can recover the values of its parameters remarkably well. We examine two popular noninformative priors and obtain very similar results, although when we use an informative, naturalness-motivated prior, we find some sizeable differences. We show that a further strong improvement in reconstructing the SU3 parameters can by achieved by applying additional information about the relic abundance at the level of WMAP accuracy, although the expected data from Planck will have only a very limited additional impact. Further external data may be required to break some remaining degeneracies. We argue that the method presented here is applicable to a wide class of low-energy effective supersymmetric models, as it does not require one to deal with purely experimental issues, e.g., detector performance, and has the additional advantages of computational efficiency. Furthermore, our approach allows one to distinguish the effect of the model's internal structure and of the external data on the final parameters constraints.
|
Xie, J. J., & Wilkin, C. (2010). Associated strangeness production in the pp -> pK(+) K(-)p and pp -> pK(+)pi(0)Sigma(0) reactions. Phys. Rev. C, 82(2), 025210–6pp.
Abstract: The total and differential cross sections for associated strangeness production in the pp -> pK(+) K(-)p and pp -> pK(+)pi(0)Sigma(0) reactions have been studied in a unified approach using an effective Lagrangian model. It is assumed that both the K(-)p and pi(0)Sigma(0) final states originate from the decay of the Lambda(1405) that was formed in the production chain pp -> p(N*(1535). K+ Lambda(1405)). The available experimental data are well reproduced, especially the ratio of the two total cross sections, which is much less sensitive to the particular model of the entrance channel. The significant coupling of the N*(1535) to Lambda(1405)K is further evidence for large ss components in the quark wave function of the N*(1535).
|
