Nuclear Theory·nucl-th

Friday·July 27, 2018

10 papers—5 primary·5 cross-listed

06
Transverse Momentum Spectra at Threshold for Groomed Heavy Quark Jets
Yiannis Makris🇺🇸 · Varun Vaidya🇺🇸
We present the transverse momentum spectrum for a heavy hadron at threshold in a groomed jet initiated by a heavy quark. The cross section is doubly differential in the energy fraction of an identified heavy hadron in the jet and its transverse momentum measured with respect to the groomed (recoil free) jet axis. The grooming is implemented using a soft-drop grooming algorithm and helps us in mitigating the effects of Non-Global logarithms and pile up. For the particular case of a $B$ meson, we identify two distinct regimes of the transverse momentum spectrum and develop an EFT within the formalisms of Soft Collineat Effective Theory (SCET) and Heavy Quark Effective Theory (HQET) for each of these regions. We show how each region can be matched smoothly into the other to provide a prediction for the perturbative transverse momentum spectrum. The EFT also predicts the scaling behavior of the leading non-perturbative power corrections and implements a simple shape function to account for hadronization. We work in the threshold region where the heavy hadron carries most of the energy of the jet since in this regime, we have a very good discriminating power between heavy quark and gluon initiated jets. We observe that the shape of the spectrum is independent of the energy of the jet over a large range of transverse momentum. We propose that this spectrum can be used as a probe of evolution for heavy quark TMD fragmentation function. At the same time, it can be treated as a jet substructure observable for probing Quark-Gluon Plasma (QGP).
↳ hep-phnucl-thJHEP(2018)·40 citations
07
Measurements of the chiral magnetic effect with background isolation in 200 GeV Au+Au collisions at STAR
Jie Zhao (for the STAR collaboration)🇺🇸
Using two novel methods, pair invariant mass ( $m_{in v}$ ) and comparative measurements with respect to reaction plane ( $Ψ_{RP}$ ) and participant plane ( $Ψ_{PP}$ ), we isolate the possible chiral magnetic effect (CME) from backgrounds in 200 GeV Au+Au collisions at STAR. The invariant mass method identifies the resonance background contributions, coupled with the elliptic flow ( $v_{2}$ ), to the charge correlator CME observable ( $Δ γ$ ). At high mass ( $m_{in v} > 1.5$ GeV/ $c^{2}$ ) where resonance contribution is small, we obtain the average $Δ γ$ magnitude. In the low mass region ( $m_{in v} < 1.5$ GeV/ $c^{2}$ ), resonance peaks are observed in $Δ γ$ ( $m_{in v}$ ). An event shape engineering (ESE) method is used to model the background shape in $m_{in v}$ to extract the potential CME signal at low $m_{in v}$ . In the comparative method, the $Ψ_{RP}$ is assessed by spectator neutrons measured by ZDC, and the $Ψ_{PP}$ by the 2 $^{n d}$ -harmonic event plane measured by the TPC. The $v_{2}$ is stronger along $Ψ_{PP}$ and weaker along $Ψ_{RP}$ ; in contrast, the magnetic field, mainly from spectator protons, is weaker along $Ψ_{PP}$ and stronger along $Ψ_{RP}$ . As a result, the $Δ γ$ measured with respect to $Ψ_{RP}$ and $Ψ_{PP}$ contain different amounts of CME and background, and can thus determine these two contributions. It is found that the possible CME signals with background isolation by these two novel methods are small, on the order of a few percent of the inclusive $Δ γ$ measurements.
↳ nucl-exhep-exhep-phnucl-thNPA(2019)·23 citations
08
Confronting nuclear equation of state in the presence of dark matter using GW170817 observation in relativistic mean field theory approach
Arpan Das🇮🇳 · Tuhin Malik🇮🇳 · Alekha C. Nayak🇮🇳
We confront admixture of dark matter inside neutron star using gravitational wave constraints coming from binary neutron star merger. We consider a relativistic mean field model including $σ - ω - ρ$ meson interaction with NL3 parameterization. We study fermionic dark matter interacting with nucleonic matter via Higgs portal mechanism. We show that admixture of dark matter inside the neutron star soften the equation state and lower the value of tidal deformability. Gravitational wave GW170817 observation puts an upper bound on tidal deformability of a binary neutron star with low spin prior at 90\% confidence level, which disfavors stiff equation of state such as Walecka model with NL3 parameterization. However, we show that Walecka model with NL3 parameterization with a fermionic dark matter component satisfy the tidal deformability bound coming from the GW170817 observation.
↳ hep-phastro-ph.COnucl-thPRD(2019)·94 citations
09
A broad pseudovector glueball from holographic QCD
Frederic Brünner🇦🇹 · Josef Leutgeb🇦🇹 · Anton Rebhan🇦🇹
We study the decay of a pseudovector glueball with quantum numbers $J^{P C} = 1^{+-}$ , the lightest glueball with spin different from zero or two, in the top-down holographic Witten-Sakai-Sugimoto model. This glueball is dual to the string-theoretic Kalb-Ramond tensor field, which completely fixes all its couplings by gauge invariance and $D$ -brane anomaly inflow. The dominant decay channels are determined by a Chern-Simons-like action for the flavor branes; couplings from the Dirac-Born-Infeld action turn out to be subdominant. While the resulting width is parametrically of order $N_{c}^{- 2} λ^{- 1}$ for $N_{c}$ colors and 't Hooft coupling $λ$ , when extrapolated to $N_{c} = 3$ and with $λ$ matched to experimental data, the prediction is that the pseudovector glueball is an extremely broad resonance.
↳ hep-phhep-thnucl-thPLB(2019)·21 citations
10
Reduced hadronic uncertainty in the determination of $V_{u d}$
Chien-Yeah Seng🇨🇳 · Mikhail Gorchtein🇩🇪 · Hiren H. Patel🇺🇸 · Michael J. Ramsey-Musolf🇺🇸
We analyze the universal radiative correction $Δ_{R}^{V}$ to neutron and superallowed nuclear $β$ decay by expressing the hadronic $γ W$ -box contribution in terms of a dispersion relation, which we identify as an integral over the first Nachtmann moment of the $γ W$ interference structure function $F_{3}^{(0)}$ . By connecting the needed input to existing data on neutrino and antineutrino scattering, we obtain an updated value of $Δ_{R}^{V} = 0.02467 (22)$ , wherein the hadronic uncertainty is reduced. Assuming other Standard Model theoretical calculations and experimental measurements remain unchanged, we obtain an updated value of $∣ V_{u d} ∣ = 0.97366 (15)$ , raising tension with the first row CKM unitarity constraint. We comment on ways current and future experiments can provide input to our dispersive analysis.
↳ hep-phnucl-exnucl-thPRL(2018)·290 citations

Affiliations

first authorsco-authorsvia INSPIRE

Transverse Momentum Spectra at Threshold for Groomed Heavy Quark Jets

Measurements of the chiral magnetic effect with background isolation in 200 GeV Au+Au collisions at STAR

Confronting nuclear equation of state in the presence of dark matter using GW170817 observation in relativistic mean field theory approach

A broad pseudovector glueball from holographic QCD

Reduced hadronic uncertainty in the determination of Vud​

Affiliations

Reduced hadronic uncertainty in the determination of $V_{u d}$