The multiplicity (N_ch) and pseudorapidity distribution (dN_ch/dη) of primary charged particles in p+p collisions at Large Hadron Collider (LHC) energies of \sqrt(s) = 10 and 14 TeV are obtained from extrapolation of existing measurements at lower \sqrt(s). These distributions are then compared to calculations from PYTHIA and PHOJET models. The existing \sqrt(s) measurements are unable to distinguish between a logarithmic and power law dependence of the average charged particle multiplicity (<N_ch>) on \sqrt(s), and their extrapolation to energies accessible at LHC give very different values. Assuming a reasonably good description of inclusive charged particle multiplicity distributions by Negative Binomial Distributions (NBD) at lower \sqrt(s) to hold for LHC energies, we observe that the logarithmic \sqrt(s) dependence of <N_ch> are favored by the models at midrapidity. The dN_ch/dηversus ηfor the existing measurements are found to be reasonably well described by a function with three parameters which accounts for the basic features of the distribution, height at midrapidity, central rapidity plateau and the higher rapidity fall-off. Extrapolation of these parameters as a function of \sqrt(s) is used to predict the pseudorapidity distributions of charged particles at LHC energies. dN_ch/dηcalculations from PYTHIA and PHOJET models are found to be lower compared to those obtained from the extrapolated dN_ch/dηversus ηdistributions for a broad ηrange.
Proton-Proton ($pp$) collisions at the Large Hadron Collider (LHC) are simulated in order to study events with a high local density of charged particles produced in narrow pseudorapidty windows of $Δη$ = 0.1, 0.2, and 0.5. The $pp$ collisions are generated at center of mass energies of $\sqrt{s} = 2.36$, $7$, $8$, and $13$ TeV, i.e. the energies at which the LHC has operated so far, using PYTHIA and HERWIG event generators. We have also studied the average of the maximum charged-particle density versus the event multiplicity for all events, using the different pseudorapidity windows. This stud…
A search is presented for new phenomena in events characterised by high jet multiplicity, no leptons (electrons or muons), and four or more jets originating from the fragmentation of $b$-quarks ($b$-jets). The search uses 139 fb$^{-1}$ of $\sqrt{s}$ = 13 TeV proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider during Run 2. The dominant Standard Model background originates from multijet production and is estimated using a data-driven technique based on an extrapolation from events with low $b$-jet multiplicity to the high $b$-jet multiplicities used in th…
The self-normalised $ψ(2S)$ yields as a function of charged-particle multiplicity in pp collisions at $\sqrt{s}$ = 13 TeV and p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$= 8.16 TeV, using the ALICE detector at the CERN LHC, are reported in these proceedings. This measurement represents one of the main tools to understand the role of multiparton interactions and their influence on charmonium production in small systems, i.e pp and pA collisions. The ratio of $ψ(2S)$-over-J/$ψ$ as a function of charged-particle multiplicity is also presented for both pp and p--Pb collisions. The comparison to th…
The production of the $K_S^0$ meson in high multiplicity $pp$ collisions at $\sqrt{s} =$ 13 TeV is investigated considering the hybrid formalism and the solution of the running coupling Balitsky - Kovchegov equation. The associated cross section is estimated and compared with the experimental data for the transverse momentum spectrum. Moreover, we analyze the self-normalized yields of $K_S^0$ mesons as a function of the multiplicity of coproduced charged hadrons and demonstrate that a steep increasing is theoretically predicted. A comparison with the ALICE data is presented considering two dis…
Multiplicity dependencies of midrapidity transverse momentum distributions of identified charged particles in inelastic proton-proton collisions at center-of-mass energy of 7 TeV at the Large Hadron Collider (LHC), measured by ALICE Collaboration, have been analyzed. The full abstract with important results on the established effective temperature versus energy density dependence, estimated critical energy densities for probable deconfinement phase transition in proton-proton collisions at center-of-mass energy of 7 and 13 TeV and other results is given in the manuscript file.
A machine learning technique is used to fit multiplicity distributions in high-energy proton-proton collisions and applied to make predictions for collisions at higher energies. The method is tested with Monte Carlo event generator events. Charged-particle multiplicity and transverse-momentum distributions within different pseudorapidity intervals in proton-proton collisions were simulated using the PYTHIA event generator for center of mass energies $\sqrt{s}$= 0.9, 2.36, 2.76, 5, 7, 8, 13 TeV for model training and validation and at 10, 20, 27, 50, 100 and 150 TeV for model predictions. Compa…
Negative binomial multiplicity distribution in proton-proton collisions in limited pseudorapidity intervals at LHC up to sqrt (s) = 7 TeV and the clan model
Multiplicity dependence of two-particle azimuthal correlations in pp collisions at the LHC
我们给出了用ALICE探测器记录的$\sqrt{s} = 0.9$、$2.76$和$7$ TeV pp碰撞中从双强子方位角关联获得的每个触发粒子的粒子对产额的测量结果。的产率作为带电粒子多重性的函数进行了研究。与单粒子产量一起，对产量提供了关于部分子在低横动量下碎裂的信息，以及多个部分子相互作用对粒子产生的贡献。将数据与使用PYTHIA6、PYTHIA8和PHOJET事件发生器的计算进行比较。
Multiplicity dependence of the entropy and heat capacity for pp collisions at LHC energies
Facultad de Ciencias Físico Matemáticas, Benemérita Universidad Autónoma de Puebla（普埃布拉自治大学物理数学科学学院）；Centro de Agroecología, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla（普埃特拉自治大学科学院农业生态学中心）
Multiplicity dependence of heavy-flavour correlations with charged particle and collective effects in p--Pb collisions at $\sqrt{s_\mathrm{NN}}$= 5.02 TeV with ALICE at LHC
Heavy quarks (charm and beauty) are produced in hard-scattering processes and the study of their production in proton--proton (pp) collisions is an important test for calculations based on perturbative Quantum Chromodynamics (pQCD). Heavy-flavor production as a function of charged-particle multiplicity provides insight into the processes occurring at the partonic level and the interplay between the hard and soft particle production mechanisms in pp collisions. In this contribution, measurements of open heavy-flavor production as a function of multiplicity, via the study of the $\mathrm{D}$-mes…
This paper presents studies of Bose-Einstein correlations (BEC) in proton-proton collisions at a centre-of-mass energy of 13 TeV, using data from the ATLAS detector at the CERN Large Hadron Collider. Data were collected in a special low-luminosity configuration with a minimum-bias trigger and a high-multiplicity track trigger, accumulating integrated luminosities of 151 $μ$b$^{-1}$ and 8.4 nb$^{-1}$ respectively. The BEC are measured for pairs of like-sign charged particles, each with $|η|$ < 2.5, for two kinematic ranges: the first with particle $p_T$ > 100 MeV and the second with particle $p…
In this contribution, the production of heavy-flavor hadrons as a function of multiplicity, via the study of the D-meson and heavy-flavor hadron decay leptons self-normalized yields in pp collisions at the center of mass energy $\sqrt{s} = 13$ TeV is discussed. Comparisons are made with similar measurements of J/$ψ$ at $\sqrt{s} = 13$ TeV and various model calculations. The $\mathrm{Λ_{c}^{+}/D^{0}}$ and $\mathrm{D^{+}_{s}/D^{0}}$ yield ratios in different multiplicity intervals in pp collisions at $\sqrt{s} = 13$ TeV are also reported. In addition, the ALICE measurement of $\mathrm{Λ_{c}^{+}}…
At the LHC collision energies, multiple parton interactions (MPI) are a key ingredient for particle production models including hard scale processes like heavy-quark production (charm and beauty). Quarkonium measurements in high-multiplicity proton-proton (pp) collisions can shed light on the role of MPI at such hard momentum scales, as well as on the interplay between hard and soft particle production mechanisms. In addition, quarkonium production measurements in minimum bias pp collisions, besides serving as a reference for heavy-ion collisions collected at the same center-of-mass energy, re…
Measurement of the multiplicity dependence of charm production in proton--proton collisions at \sqrt{s}=7 TeV with the ALICE experiment at the CERN-LHC
Gluon saturation and energy dependence of hadron multiplicity in pp and AA collisions at the LHC
ALICE合作组在大型强子对撞机（LHC）上进行的\sqrt{s} =2.76 TeV Pb+Pb碰撞的最新结果表明，Pb+Pb碰撞中带电强子多重数的能量依赖性与p+p碰撞中的有很大不同.我们表明，这种不同的能量依赖性可以解释列入一个强的角度排序的胶子衰变级联内的颜色玻璃凝聚（或胶子饱和）的方法。这种效应在饱和尺度大于1 GeV的核-核碰撞中更为重要。我们的公式很好地描述了p+p和Pb+Pb碰撞的LHC数据。
De-Confinement in high multiplicity proton-proton collisions at LHC energies
最近，CMS协作组发表了在LHC能量$\sqrt s $ = 0.9-13 TeV的高多重数事件中确定的粒子横动量谱。本文在高能强子碰撞中产生的重叠弦团簇内部色场的框架下分析了横向动量谱。非阿贝尔性质反映在色场的相干和中，其结果是引起横向动量的增强和相对于非重叠弦的多重性的抑制。得到了初始温度和剪切粘度与熵密度之比$η/s$。对于较高的多重性事件在$\sqrt s $ =7和13 TeV的初始温度高于普遍强子化温度，是一致的，与创建的de-confined物质。在这些小系统中，可以认为热化是量子隧穿通过由限制色场引入的事件视界的结果，类似于霍金-昂鲁效应。在临界温度附近，小的剪切粘度与熵密度之比$η/s$表明该物质是强耦合的夸克-胶子等离子体。
Heavy Quark Energy Loss in High Multiplicity Proton Proton Collisions at LHC
研究高能核碰撞中产生的退禁闭物质最有希望的方法之一是（重）夸克的能量损失。在相对论重离子对撞机（RHIC）的实验中已经表明，即使是粲夸克和底夸克，尽管它们的质量很高，在夸克-胶子等离子体中也会经历显著的介质抑制。在这个探索性的研究中，我们研究了在LHC能区的高多重数质子-质子碰撞中重夸克的能量损失。虽然碰撞系统比RHIC（p+p vs. Au+Au）小，但更高的能量可能导致与RHIC的Cu+Cu碰撞相当的多重性。最近，CMS的合作表明，这些粒子可能相互作用。粲夸克与这种环境的相互作用引起了不可忽视的抑制高动量重夸克在基本碰撞。
Multiplicity and pseudorapidity ($η$) density ($dN_{\rm ch}/dη$) distributions of charged hadrons provide key information towards understanding the particle production mechanisms and initial conditions of high-energy heavy-ion collisions. However, detector constraints limit the $η$-range across which charged particle measurements can be carried out. Extrapolating the measured distributions to large $η$-range by parameterizing measured distributions and by using calculations from event generators, we characterize the production of charged particles over the full kinematic range. In the present …
The comparisons of the charged-particle multiplicity and the average transverse momentum distributions on the scaled multiplicity, KNO scale, using the results of the ATLAS collaboration at the LHC are presented. These distributions were measured in proton-proton collisions at centre-of-mass energies from 0.9 to 13 TeV for the absolute pseudorapidity region less than 2.5 and two samples of events with each charged-particle transverse momentum greater than 100 and 500 MeV, respectively. The shape evolution of the multiplicity distributions with a collision energy is studied in terms of KNO scal…
