Mixing stops at the LHC

We study the phenomenology of a light stop NLSP in the presence of large mixing with either the first or the second generation. R-symmetric models provide a prime setting for this scenario, but our discussion also applies to the MSSM when a significant amount of mixing can be accommodated. In our framework the dominant stop decay is through the flavor violating mode into a light jet and the LSP in an extended region of parameter space. There are currently no limits from ATLAS and CMS in this region. We emulate shape-based hadronic SUSY searches for this topology, and find that they have potential sensitivity. If the extension of these analyses to this region is robust, we find that these searches can set strong exclusion limits on light stops. If not, then the flavor violating decay mode is challenging and may represent a blind spot in stop searches even at 13 TeV. Thus, an experimental investigation of this scenario is well motivated

On Lagrangian approach to self-dual gauge fields in spacetime of nontrivial topology

We study the Lagrangian description of chiral bosons, p-form gauge fields with (anti–)self-dual gauge field strengths, in D = 2 p + 2 dimensional spacetime of non-trivial topology. We show that the manifestly Lorentz and diffeomorphism invariant Pasti-Sorokin-Tonin (PST) approach is consistent and produces the (anti-)self-duality equation also in topologically nontrivial spacetime. We discuss in what circumstances the nontrivial topology makes difference between two disconnected, da-timelike and da-spacelike branches of the PST system, the gauge fixed version of which are described by not manifestly invariant Henneaux-Teitelboim (HT) and Perry-Schwarz (PS) actions, respectively

In-Pile 4He Source for UCN Production at the ESS

ESS will be a premier neutron source facility. Unprecedented neutron beam intensities are ensured by spallation reactions of a 5 MW, 2.0 GeV proton beam impinging on a tungsten target equipped with advanced moderators. The work presented here aims at investigating possibilities for installing an ultra cold neutron (UCN) source at the ESS. One consequence of using the recently proposed flat moderators is that they take up less space than the moderators originally foreseen and thus leave more freedom to design a UCN source, close to the spallation hotspot. One of the options studied is to place a large 4He UCN source in a through-going tube which penetrates the shielding below the target. First calculations of neutron flux available for UCN production are given, along with heat-load estimates. It is estimated that the flux can give rise to a UCN production at a rate of up to <math id="M1" xmlns="http://www.w3.org/1998/Math/MathML"><mn mathvariant="normal">1.5</mn><mo>·</mo><msup><mrow><mn mathvariant="normal">10</mn></mrow><mrow><mn mathvariant="normal">8</mn></mrow></msup></math>  UCN/s. A production in this range potentially allows for a number of UCN experiments to be carried out at unprecedented precision, including, for example, quantum gravitational spectroscopy with UCNs which rely on high phase-space density

Analog geometry in an expanding fluid from AdS/CFT perspective

The dynamics of an expanding hadron fluid at temperatures below the chiral transition is studied in the framework of AdS/CFT correspondence. We establish a correspondence between the asymptotic AdS geometry in the 4+1 dimensional bulk with the analog spacetime geometry on its 3+1 dimensional boundary with the background fluid undergoing a spherical Bjorken type expansion. The analog metric tensor on the boundary depends locally on the soft pion dispersion relation and the four-velocity of the fluid. The AdS/CFT correspondence provides a relation between the pion velocity and the critical temperature of the chiral phase transition

Constraints on Heavy Neutrino and SUSY Parameters Derived from the Study of Neutrinoless Double Beta Decay

New constraints on the lepton number violating (LNV) parameters are derived from the analysis of the neutrinoless double beta ( <math id="M1" xmlns="http://www.w3.org/1998/Math/MathML"><mn mathvariant="normal">0</mn><mi>ν</mi><mi>β</mi><mi>β</mi></math> ) decay in the hypothesis that this process would occur through the exchange of heavy neutrinos and/or SUSY particles. For derivation, we use new values of both phase space factors (PSFs) and nuclear matrix elements (NMEs) calculated with numerical codes developed recently, as well as the most recent experimental lifetimes. The NMEs are computed with a shell model (ShM) code for <math id="M2" xmlns="http://www.w3.org/1998/Math/MathML"><msup><mrow><mi mathvariant="normal"> </mi></mrow><mrow><mn>48</mn></mrow></msup><mtext>C</mtext><mtext>a</mtext></math> , <math id="M3" xmlns="http://www.w3.org/1998/Math/MathML"><msup><mrow><mi mathvariant="normal"> </mi></mrow><mrow><mn>76</mn></mrow></msup><mtext>G</mtext><mtext>e</mtext></math> , and <math id="M4" xmlns="http://www.w3.org/1998/Math/MathML"><msup><mrow><mi mathvariant="normal"> </mi></mrow><mrow><mn>82</mn></mrow></msup><mtext>S</mtext><mtext>e</mtext></math> nuclei, while at present similar ShM results are available only for the first nucleus. We compare our results with similar ones from literature, obtained with ShM, QRPA, and IBM-2 methods, and conclude that more results are needed for a relevant analysis on the validity of NMEs associated with these decay mechanisms

W ′ signatures with odd Higgs particles

We point out that W ′ bosons may decay predominantly into Higgs particles associated with their broken gauge symmetry. We demonstrate this in a renormalizable model where the W ′ and W couplings to fermions differ only by an overall normalization. This “meta-sequential” W ′ boson decays into a scalar pair, with the charged one subsequently decaying into a W boson and a neutral scalar. These scalars are odd under a parity of the Higgs sector, which consists of a complex bidoublet and a doublet. The W ′ and Z ′ bosons have the same mass and branching fractions into scalars, and may show up at the LHC in final states involving one or two electroweak bosons and missing transverse energy

Azimuthal harmonics of color fields in a high energy nucleus

Recent experimental results have revealed a surprisingly rich structure of multiparticle azimuthal correlations in high energy proton–nucleus collisions. Final state collective effects can be responsible for many of the observed effects, but it has recently been argued that a part of these correlations are present already in the wavefunctions of the colliding particles. We evaluate the momentum space 2-particle cumulant azimuthal anisotropy coefficients vn{2} , n=2,3,4 from fundamental representation Wilson line distributions describing the high energy nucleus. These would correspond to the flow coefficients in very forward proton–nucleus scattering. We find significant differences between Wilson lines from the MV model and from JIMWLK evolution. The magnitude and qualitative transverse momentum dependence of the vn{2} values suggest that the fluctuations present in the initial fields are a significant contribution to the observed anisotropies

The massive fermion phase for the U(N) Chern-Simons gauge theory in D=3 at large N

We explore the phase structure of fermions in the U(N) Chern-Simons Gauge theory in three dimensions using the large N limit where N is the number of colors and the fermions are taken to be in the fundamental representation of the U(N) gauge group. In the large N limit, the theory retains its classical conformal behavior and considerable attention has been paid to possible AdS/CFT dualities of the theory in the conformal phase. In this paper we present a solution for the massive phase of the fermion theory that is exact to the leading order of ‘t Hooft’s large N expansion. We present evidence for the spontaneous breaking of the exact scale symmetry and analyze the properties of the dilaton that appears as the Goldstone boson of scale symmetry breaking

The Study of Thermal Conditions on Weibel Instability

Weibel electromagnetic instability has been studied analytically in relativistic plasma with high parallel temperature, where <math id="M1" xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">|</mo><mi>α</mi><mo>=</mo><mo stretchy="false">(</mo><mrow><mrow><mi>m</mi><msup><mrow><mi>c</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow><mo>/</mo><mrow><msub><mrow><mi>T</mi></mrow><mrow><mo stretchy="false">∥</mo></mrow></msub></mrow></mrow><mo stretchy="false">)</mo><mo stretchy="false">(</mo><mn>1</mn><mo>+</mo><mrow><mrow><msup><mrow><msub><mrow><mover accent="true"><mrow><mi>p</mi></mrow><mo>^</mo></mover></mrow><mrow><mo>⊥</mo></mrow></msub></mrow><mrow><mn>2</mn></mrow></msup></mrow><mo>/</mo><mrow><msup><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msup><msup><mrow><mi>c</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></mrow><msup><mrow><mo stretchy="false">)</mo></mrow><mrow><mrow><mrow><mn>1</mn></mrow><mo>/</mo><mrow><mn>2</mn></mrow></mrow></mrow></msup><mo stretchy="false">|</mo><mo>≪</mo><mn>1</mn></math> and while the collision effects of electron-ion scattering have also been considered. According to these conditions, an analytical expression is derived for the growth rate of the Weibel instability for a limiting case of <math id="M2" xmlns="http://www.w3.org/1998/Math/MathML"><mo stretchy="false">|</mo><mi>ζ</mi><mo>=</mo><msqrt><mrow><mrow><mi>α</mi></mrow><mo>/</mo><mrow><mn>2</mn></mrow></mrow></msqrt><mo stretchy="false">(</mo><mrow><mrow><msup><mrow><mi>ω</mi></mrow><mrow><mi>′</mi></mrow></msup></mrow><mo>/</mo><mrow><mi>c</mi><mi>k</mi></mrow></mrow><mo stretchy="false">)</mo><mo stretchy="false">|</mo><mo>≪</mo><mn>1</mn></math> , where <math id="M3" xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mrow><mi>ω</mi></mrow><mrow><mi>′</mi></mrow></msup></mrow></math> is the sum of the wave frequency of instability and the collision frequency of electrons with background ions. The results show that in the limiting condition <math id="M4" xmlns="http://www.w3.org/1998/Math/MathML"><mi>α</mi><mo>≪</mo><mn>1</mn></math> there is an unusual situation of the Weibel instability so that <math id="M5" xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow><mi>T</mi></mrow><mrow><mo stretchy="false">∥</mo></mrow></msub><mo>≫</mo><msub><mrow><mi>T</mi></mrow><mrow><mo>⊥</mo></mrow></msub></math> , while in the classic Weibel instability <math id="M6" xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow><mi>T</mi></mrow><mrow><mo stretchy="false">∥</mo></mrow></msub><mo>≪</mo><msub><mrow><mi>T</mi></mrow><mrow><mo>⊥</mo></mrow></msub></math> . The obtained results show that the growth rate of the Weibel instability will be decreased due to an increase in the number of collisions and a decrease in the anisotropic temperature by the increasing of plasma density, while the increase of the parameter <math id="M7" xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow><mover accent="true"><mrow><mi>γ</mi></mrow><mo>^</mo></mover></mrow><mrow><mo>⊥</mo></mrow></msub><mo>=</mo><mo stretchy="false">(</mo><mn>1</mn><mo>+</mo><mrow><mrow><msup><mrow><msub><mrow><mover accent="true"><mrow><mi>p</mi></mrow><mo>^</mo></mover></mrow><mrow><mo>⊥</mo></mrow></msub></mrow><mrow><mn>2</mn></mrow></msup></mrow><mo>/</mo><mrow><msup><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msup><msup><mrow><mi>c</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></mrow><msup><mrow><mo stretchy="false">)</mo></mrow><mrow><mrow><mrow><mn>1</mn></mrow><mo>/</mo><mrow><mn>2</mn></mrow></mrow></mrow></msup></math> leads to the increase of the Weibel instability growth rate