118803187
Angular momentum decomposition from a QED example
We investigate the angular momentum decomposition with a quantum electrodynamics example to clarify the proton spin decomposition debates. We adopt the light-front formalism where the parton model is well defined. We prove that the sum of fermion and boson angular momenta is equal to half the sum of the two gravitational form factors $A(0)$ and $B(0)$, as is well known. However, the suggestion to make a separation of the above relation into the fermion and boson pieces, as a way to measure the orbital angular momentum of fermions or bosons, respectively, is not justified from our explicit calculation.
119232315
Quark orbital motions from Wigner distributions
We investigate quark Wigner distributions in a light-cone spectator model. Both the scalar and the axial-vector spectators are included. The light-cone wave functions are derived from effective quark-spectator-nucleon vertex and then generalized by adjusting the power of energy denominators. The gauge link is taken into account by introducing relative phases to the light-cone amplitudes, and the phases are estimated from one gluon exchange interactions. The mixing distributions, which describe the correlation between transverse coordinate and transverse momentum and represent quark orbital motions, are calculated from the Wigner distributions. We find both $u$ quark and $d$ quark have positive orbital angular momentum in a polarized proton at small $x$ region, but a sign change is observed at large $x$ region for the $d$ quark. Besides, some model relations between Wigner distributions with different polarization configurations are found.
118430959
Quark angular momentum in a spectator model
Abstract We investigate the quark angular momentum in a model with the nucleon being a quark and a spectator. Both scalar and axial-vector spectators are included. We perform the calculations in the light-cone formalism where the parton concept is well defined. We calculate the quark helicity and canonical orbital angular momentum. Then we calculate the gravitational form factors which are often related to the kinetic angular momentums, and find that even in a no gauge field model we cannot identify the canonical angular momentums with half the sum of gravitational form factors. In addition, we examine the model relation between the orbital angular momentum and pretzelosity, and find it is violated in the axial-vector case.
15092713
A serializer ASIC for high speed data transmission in cryogenic and HiRel environment
A high speed 16:1 serializer ASIC has been developed using a commercial 0.25 μm silicon-on-sapphire CMOS technology. At room temperature the ASIC operates from 4.0 to 5.7 Gbps with power consumption of 463 mW. The total jitter is 62 ps at the bit error rate of 10−12 at 5 Gbps. A 200-MeV proton beam test indicates that the ASIC is suitable for high energy physics applications. A liquid nitrogen temperature test indicates that the ASIC may be used at cryogenic temperature applications. The reliability of the serializer at liquid nitrogen temperature is to be studied. A 6-lane serializer array with 10 Gbps/lane with redundancy capability is under development.
44596378
Unraveling the physics behind modified Higgs couplings: LHC versus a Higgs factory
Strongly modified $h\ensuremath{\gamma}\ensuremath{\gamma}$ and $hgg$ couplings indicate new electroweak and color mediators, respectively, with a light mass and a significant coupling to the Higgs boson. We point out the Higgs boson could have a significant decay width into the mediators. This represents one new class of exotic Higgs decay possibilities: off-shell exotic Higgs decays. We then propose uncovering the hidden new physics through such exotic decays. A great advantage of this strategy is that we can directly probe the couplings between the Higgs boson and the mediators, which is hard to achieve by using other methods. Focusing on the electroweak mediators, we study a simplified model using as an example final states with tau leptons and neutrinos. Because one of the mediators is off shell and its decay products are extremely soft, it is challenging to make a discovery at the Large Hadron Collider. A Higgs factory such as the International Linear Collider, however, could serve as a discovery machine for such exotic Higgs decays even in an early stage.
119264713
Measuring Di-Higgs Physics via the $t \bar t hh \to t \bar t b \bar bb\bar b$ Channel
The measurement of di-Higgs physics can provide crucial information on electroweak phase transition in the early Universe and significant clues on new physics coupling with the Higgs field directly. This measurement has been suggested to be pursued mainly via the $pp \to hh$ production. In this letter, we propose a new strategy to do that, i.e., via the $pp \to t \bar t hh $ production. Because of its positive correlation with the rescaled tri-Higgs coupling $\frac{\lambda}{\lambda_{\rm SM}}$ (in comparison to a negative one for the $pp \to hh$ production) in the neighborhood of $\frac{\lambda}{\lambda_{\rm SM}} \sim 1$, the $pp \to t\bar t hh$ production complements the $pp \to hh$ one in measuring di-Higgs physics, particularly for $\frac{\lambda}{\lambda_{\rm SM}}>1$, at both the High Luminosity LHC (HL-LHC) and a next-generation $pp$-collider. As an illustration, we work on the process $pp\to t\bar thh \to t\bar t b\bar b b\bar b$. We show that a statistical significance of $> 2.0 \sigma$ at the HL-LHC, comparable to that of the $pp \to hh \to b\bar b \gamma\gamma$ channel, and a statistical significance of $\sim 5 \sigma$ at a 100 TeV $pp$-collider, with 3000 fb$^{-1}$ of data, are achievable in searching for the di-Higgs production with $\frac{\lambda}{\lambda_{\rm SM}} = 1$.
118915813
Supersymmetric Pati–Salam models from intersecting D6-branes: a road to the Standard Model
Abstract We provide a systematic construction of three-family N = 1 supersymmetric Pati–Salam models from Type IIA orientifolds on T 6 / ( Z 2 × Z 2 ) with intersecting D6-branes. All the gauge symmetry factors SU ( 4 ) C × SU ( 2 ) L × SU ( 2 ) R arise from the stacks of D6-branes with U ( n ) gauge symmetries, while the “hidden sector” is specified by USp ( n ) branes, parallel with the orientifold planes or their Z 2 images. The Pati–Salam gauge symmetry can be broken down to the SU ( 3 ) C × SU ( 2 ) L × U ( 1 ) B − L × U ( 1 ) I 3 R via D6-brane splittings, and further down to the Standard Model via D- and F-flatness preserving Higgs mechanism from massless open string states in a N = 2 subsector. The models also possess at least two confining hidden gauge sectors, where gaugino condensation can in turn trigger supersymmetry breaking and (some) moduli stabilization. The systematic search yields 11 inequivalent models: 8 models with less than 9 Standard Model Higgs doublet-pairs and 1 model with only 2 Standard Model Higgs doublet-pairs, 2 models possess at the string scale the gauge coupling unification of SU ( 2 ) L and SU ( 2 ) R , and all the models possess additional exotic matters. We also make preliminary comments on phenomenological implications of these models.
119231771
Multiple b -jets reveal top superpartners and the 125 GeV Higgs
We demonstrate that in supersymmetry (SUSY) with relatively light top superpartners, h -> bb can be a very promising channel to discover the SM-like Higgs resonance at the Large Hadron Collider (LHC), although in general contexts it is thought to be challenging because of its huge QCD background. In this scenario, the SM-like Higgs boson is mainly produced via cascade decays initiated by pair-produced stop or sbottom squarks. The good sensitivity to h -> bb owes a great deal to the application of multiple (>= 4) b-jet tagging in removing the QCD background, and color-flow variables for reconstructing the Higgs resonance. We show in two benchmark points that a SM-like Higgs resonance can be discovered at the 14 TeV LHC (with a signal-to-background ratio as high as 0.35), with ~< 40/fb of data. Potentially, this strategy can be also applied to non-SUSY theories with cascade decays of top partners for the SM-like Higgs search, such as little Higgs, composite Higgs, and Randall-Sundrum models.