At leading order in the QCD coupling constant, we compute the energy loss per traveling distance of a heavy quark <math><mi>d</mi><mi>E</mi><mo>/</mo><mi>d</mi><mi>z</mi></math> from elastic scattering off thermal quarks and gluons at a temperature <math><mi>T</mi></math>, including the thermal perturbative description of soft scatterings (<math><mo>−</mo><mi>t</mi><mo>&lt;</mo><mo>−</mo><msup><mi>t</mi><mo>*</mo></msup></math>) and a perturbative QCD-based calculation for hard collisions (<math><mo>−</mo><mi>t</mi><mo>&gt;</mo><mo>−</mo><msup><mi>t</mi><mo>*</mo></msup></math>). Within this soft-hard factorization model, we find that the full results of <math><mi>d</mi><mi>E</mi><mo>/</mo><mi>d</mi><mi>z</mi></math> behaves a mild sensitivity to the intermediate cutoff <math><msup><mi>t</mi><mo>*</mo></msup></math>, supporting the validity of the soft-hard approach within the temperature region of interest. We rederive the analytic formula for <math><mi>d</mi><mi>E</mi><mo>/</mo><mi>d</mi><mi>z</mi></math> in the high-energy approximation, <math><msub><mi>E</mi><mn>1</mn></msub><mo>≫</mo><msubsup><mi>m</mi><mn>1</mn><mn>2</mn></msubsup><mo>/</mo><mi>T</mi></math>, where <math><msub><mi>E</mi><mn>1</mn></msub></math> is the injected heavy quark energy and <math><msub><mi>m</mi><mn>1</mn></msub></math> is its mass. It is realized that the soft logarithmic contribution, <math><mi>d</mi><mi>E</mi><mo>/</mo><mi>d</mi><mi>z</mi><mo>∝</mo><mi>ln</mi><mo>(</mo><mo>−</mo><msup><mi>t</mi><mo>*</mo></msup><mo>/</mo><msubsup><mi>m</mi><mi>D</mi><mn>2</mn></msubsup><mo>)</mo></math>, arises from the <math><mi>t</mi></math>-channel scattering off thermal partons, while the hard logarithmic term, <math><mi>d</mi><mi>E</mi><mo>/</mo><mi>d</mi><mi>z</mi><mo>∝</mo><mi>ln</mi><mo>[</mo><msub><mi>E</mi><mn>1</mn></msub><mi>T</mi><mo>/</mo><mo>(</mo><mo>−</mo><msup><mi>t</mi><mo>*</mo></msup><mo>)</mo><mo>]</mo></math>, stems from the <math><mi>t</mi></math>-channel scattering off thermal partons, and the one <math><mi>d</mi><mi>E</mi><mo>/</mo><mi>d</mi><mi>z</mi><mo>∝</mo><mi>ln</mi><mo>(</mo><msub><mi>E</mi><mn>1</mn></msub><mi>T</mi><mo>/</mo><msubsup><mi>m</mi><mn>1</mn><mn>2</mn></msubsup><mo>)</mo></math> comes from the <math><mi>s</mi></math>- and <math><mi>u</mi></math>-channel scattering off gluons. The sum of these contributions cancels the <math><msup><mi>t</mi><mo>*</mo></msup></math>-dependence as observed in the full result. The mass hierarchy is observed <math><mrow><mi>d</mi><mi>E</mi><mo>/</mo><mi>d</mi><mi>z</mi><mo>(</mo><mtext>charm</mtext><mo>)</mo><mo>&gt;</mo><mi>d</mi><mi>E</mi><mo>/</mo><mi>d</mi><mi>z</mi><mo>(</mo><mtext>bottom</mtext><mo>)</mo></mrow></math>. Our full results are crucial for a better description of heavy quark transport in QCD medium, in particular at low and moderate energy. We also calculate the energy loss by imposing the Einstein’s relationship. The related results appear to be systematically larger than that without imposing the Einstein’s relationship.

China

Jiazhen Peng

Kewei Yu

Shuang Li

Wei Xiong

Fei Sun

Wei Xie

Unraveling the collisional energy loss of a heavy quark in a quark-gluon plasma

We investigate the elastic photon-proton and photon-photon scattering in a holographic QCD model, focusing on the Regge regime. Considering contributions of the Pomeron and Reggeon exchange, the total and differential cross sections are calculated. While our model involves several parameters, by virtue of the universality of the Pomeron and Reggeon, for most of them the values determined in the preceding study on the proton-proton and proton-antiproton scattering can be employed. Once the two adjustable parameters, the Pomeron-photon and Reggeon-photon coupling constant, are determined with the experimental data of the total cross sections, predicting the both cross sections in a wide kinematic region, from the GeV to TeV scale, becomes possible. We show that the total cross section data can be well described within the model, and our predictions for the photon-proton differential cross section are consistent with the data.

Akira Watanabe

Zabihullah Ahmadi

Zhibo Liu

Holographic description of elastic photon-proton and photon-photon scattering

The total and differential cross sections of elastic proton-proton and proton-antiproton scattering are studied in a holographic QCD model, considering the Pomeron and Reggeon exchanges in the Regge regime. In our model setup, the Pomeron and Reggeon exchanges are described by the Reggeized spin-2 glueball and vector meson propagators, respectively. How those contributions change with the energy is explicitly shown, focusing on the contribution ratios. The adjustable parameters included in the model are determined with the experimental data, and it is presented that the resulting total and differential cross sections are consistent with the data in a wide kinematic region.

Pomeron and Reggeon contributions to elastic proton-proton and proton-antiproton scattering in holographic QCD

The total and differential cross sections of high-energy pion-proton and pion-pion scattering are investigated in a holographic QCD model, focusing on the Regge regime in which the Pomeron exchange gives the dominant contribution to those cross sections. The Pomeron is described by the Reggeized spin-2 particle propagator, and the hadron-Pomeron couplings are given by gravitational form factors of the hadrons, which are obtained from the bottom-up AdS/QCD models. Since the parameters, which characterize the Pomeron trajectory, have been determined in a preceding study of the proton-proton scattering, the pion-proton cross sections can be expressed with a single adjustable parameter. Once this parameter is determined by the experimental data of the pion-proton total cross section, its differential cross section and the pion-pion cross sections can be calculated without any additional parameter. Although the currently available data are limited, it is found that our calculation is consistent with those. Our predictions are explicitly shown, and the present model can be tested at the future experimental facilities.

Elastic pion-proton and pion-pion scattering at high energies in holographic QCD

By utilizing a soft-hard factorized model, which combines a thermal perturbative description of soft scatterings and a perturbative QCD-based calculation for hard collisions, we study the energy and temperature dependence of the heavy quark diffusion coefficients in Langevin dynamics. The adjustable parameters are fixed from the comprehensive model-data comparison. We find that a small value of the spatial diffusion coefficient at transition temperature is preferred by data  $$2\pi TD_{s}(T_{c}) \simeq 6$$  <math> <mrow> <mn>2</mn> <mi>π</mi> <mi>T</mi> <msub> <mi>D</mi> <mi>s</mi> </msub> <mrow> <mo>(</mo> <msub> <mi>T</mi> <mi>c</mi> </msub> <mo>)</mo> </mrow> <mo>≃</mo> <mn>6</mn> </mrow> </math>  . With the parameter-optimized model, we are able to describe simultaneously the prompt  $$D^{0}$$  <math> <msup> <mi>D</mi> <mn>0</mn> </msup> </math>    $$R_{\mathrm{AA}}$$  <math> <msub> <mi>R</mi> <mi>AA</mi> </msub> </math>   and  $$v_{\mathrm{2}}$$  <math> <msub> <mi>v</mi> <mn>2</mn> </msub> </math>   data at  $$p_{\mathrm{T}}\le 8$$  <math> <mrow> <msub> <mi>p</mi> <mi>T</mi> </msub> <mo>≤</mo> <mn>8</mn> </mrow> </math>   GeV in Pb–Pb collisions at  $$\sqrt{s_{\mathrm{NN}}}=2.76$$  <math> <mrow> <msqrt> <msub> <mi>s</mi> <mi>NN</mi> </msub> </msqrt> <mo>=</mo> <mn>2.76</mn> </mrow> </math>   and  $$\sqrt{s_{\mathrm{NN}}}=5.02$$  <math> <mrow> <msqrt> <msub> <mi>s</mi> <mi>NN</mi> </msub> </msqrt> <mo>=</mo> <mn>5.02</mn> </mrow> </math>   TeV. We also make predictions for non-prompt  $$D^{0}$$  <math> <msup> <mi>D</mi> <mn>0</mn> </msup> </math>   meson for future experimental tests down to the low momentum region.

Langevin dynamics of heavy quarks in a soft-hard factorized approach

It is believed that there are more fundamental gauge symmetries beyond those described by the Standard Model of particle physics. The scales of these new gauge symmetries are usually too high to be reachable by particle colliders. Considering that the phase transition (PT) relating to the spontaneous breaking of new gauge symmetries to the electroweak symmetry might be strongly first order, we propose considering the stochastic gravitational waves (GW) arising from this phase transition as an indirect way of detecting these new fundamental gauge symmetries. As an illustration, we explore the possibility of detecting the stochastic GW generated from the PT of 
					 in the space-based interferometer detectors. Our study demonstrates that the GW energy spectrum is reachable by the LISA, Tianqin, Taiji, BBO, and DECIGO experiments only for the case where the spontaneous breaking of 
					 is triggered by at least two electroweak singlet scalars.
				

Wei Chao

Wen-Feng Cui

Huai-Ke Guo

Jing Shu

Gravitational wave imprint of new symmetry breaking JS is Supported by the National Natural Science Foundation of China (11647601, 11690022, 11675243) and also Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB23030100). Wei Chao is Supported by the National Natural Science Foundation of China (11775025)

The cross sections of the high energy proton-proton scattering are studied in a holographic QCD model, focusing on the Regge regime. In our model setup, the involved nonperturbative partonic dynamics is described by the Pomeron exchange, which is realized by applying the Reggeized spin-2 particle propagator together with the proton gravitational form factor obtained from the bottom-up AdS/QCD model. Our model includes three adjustable parameters which are to be fitted by experimental data. We show that both the resulting differential and total cross sections are consistent with data, including the ones recently measured at   <math> <msqrt> <mi>s</mi> </msqrt> </math>  $$ \sqrt{s} $$  = 13 TeV by the TOTEM collaboration at the LHC. Our results imply that the present framework works well in the considered TeV scale, and further applications to other high energy scattering processes, in which the involved strong interaction can be approximated by the Pomeron exchange, are possible.

Mei Huang

Elastic proton-proton scattering at LHC energies in holographic QCD

A dedicated search is presented for new phenomena in inclusive 8- and 10-jet final states with low missing transverse momentum, with and without identification of jets originating from b quarks. The analysis is based on data from proton–proton collisions corresponding to an integrated luminosity of 19.7fb−1 collected with the CMS detector at the LHC at s=8TeV . The dominant multijet background expectations are obtained from low jet multiplicity control samples. Data agree well with the standard model background predictions, and limits are set in several benchmark models. Colorons (axigluons) with masses between 0.6 and 0.75 (up to 1.15) TeV are excluded at 95% confidence level. Similar exclusion limits for gluinos in R -parity violating supersymmetric scenarios are from 0.6 up to 1.1 TeV. These results comprise the first experimental probe of the coloron and axigluon models in multijet final states.

Armenia

Vardan Khachatryan

Albert M Sirunyan

Armen Tumasyan

Austria

Wolfgang Adam

Ece Aşılar

Thomas Bergauer

Johannes Brandstetter

Erica Brondolin

Marko Dragicevic

Janos Erö

Martin Flechl

Markus Friedl

Rudolf Fruehwirth

Vasile Mihai Ghete

Christian Hartl

Natascha Hörmann

Josef Hrubec

Manfred Jeitler

Axel König

Ilse Krätschmer

Dietrich Liko

Takashi Matsushita

Ivan Mikulec

Dinyar Rabady

Navid Rad

Babak Rahbaran

Herbert Rohringer

Jochen Schieck

Josef Strauss

Wolfgang Treberer-Treberspurg

Wolfgang Waltenberger

Claudia-Elisabeth Wulz

Belarus

Vladimir Mossolov

Nikolai Shumeiko

Juan Suarez Gonzalez

Belgium

Sara Alderweireldt

Eddi A De Wolf

Xavier Janssen

Jasper Lauwers

Merijn Van De Klundert

Hans Van Haevermaet

Pierre Van Mechelen

Nick Van Remortel

Alex Van Spilbeeck

Shimaa Abu Zeid

Freya Blekman

Jorgen D'Hondt

Nadir Daci

Isabelle De Bruyn

Kevin Deroover

Natalie Heracleous

Steven Lowette

Seth Moortgat

Lieselotte Moreels

Annik Olbrechts

Quentin Python

Stefaan Tavernier

Walter Van Doninck

Petra Van Mulders

Isis Van Parijs

Hugues Brun

Cécile Caillol

Barbara Clerbaux

Gilles De Lentdecker

Hugo Delannoy

Giuseppe Fasanella

Laurent Favart

Reza Goldouzian

Anastasia Grebenyuk

Georgia Karapostoli

Thomas Lenzi

Alexandre Léonard

Jelena Luetic

Thierry Maerschalk

Andrey Marinov

Aidan Randle-conde

Tomislav Seva

Catherine Vander Velde

Pascal Vanlaer

Ryo Yonamine

Florian Zenoni

Fengwangdong Zhang

Anna Cimmino

Tom Cornelis

Didar Dobur

Alexis Fagot

Guillaume Garcia

Muhammad Gul

Deniz Poyraz

Sinem Salva Diblen

Robert Schöfbeck

Michael Tytgat

Ward Van Driessche

Efe Yazgan

Nicolas Zaganidis

Hamed Bakhshiansohi

France

Camille Beluffi

Olivier Bondu

Sébastien Brochet

Giacomo Bruno

Search for new phenomena in events with high jet multiplicity and low missing transverse momentum in proton–proton collisions at s=8TeV

A new Hamiltonian model is introduced to study the spectrum of light hadrons. It combines relativistic field theory with elements of the constituent quark model. In addition to the standard linear confining and pseudoscalar meson exchange interactions with predetermined parameters, an additional interaction with different covariant spin structures is examined. Using a large scale Monte Carlo variational procedure, the resulting model Hamiltonian provides a very good, unified description of the light quark baryon (both octet and decuplet) and meson spectra.

Ping Wang

Unified Hamiltonian model for mesons and baryonsSupported by National Natural Science Foundation of China (11261130311, 11035006)