Nuclear modification factors from the CMS experiment

Lee, Yen-Jie

doi:10.1088/0954-3899/38/12/124015

Cited by 23 publications

(36 citation statements)

References 35 publications

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“…The level of suppression is of the same order of magnitude as charged hadrons as observed on Fig. 1 (right) where the non-prompt J/ψ R AA is plotted as a function of p T for 0-20% while the bosons and charged hadrons are presented as a function of the transverse mass for 0-10% [18]. [20] up to p T = 8 GeV/c 2 .…”

Section: B→ J/ψsupporting

confidence: 66%

Quarkonia measurements by the CMS experiment in PbPb collisions

Silvestre¹

2012

Proceedings of XXIst International Europhysics Conference on High Energy Physics — PoS(EPS-HEP2011)

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Section: B→ J/ψsupporting

confidence: 66%

Quarkonia measurements by the CMS experiment in PbPb collisions

Silvestre¹

2012

Proceedings of XXIst International Europhysics Conference on High Energy Physics — PoS(EPS-HEP2011)

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“…The results for central (0 − 5%) leadlead collisions at √ s = 2.76 TeV are shown by the dashed curve in Fig. 8, compared with new data from the ALICE [48] and CMS [49,50] experiments, extended to higher values of p T than those in [41]. /fm.…”

Section: A Quenching Of High-pt Hadronsmentioning

confidence: 99%

“…The results plotted by dashed curves are compared with data taken at different centralities of collision by the ALICE experiment [48] in Fig. 9, and by the CMS experiment [49,50] in Fig. 10.…”

Section: A Quenching Of High-pt Hadronsmentioning

confidence: 99%

Quenching of high-pThadrons: Energy loss versus color transparency

et al. 2012

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High-pT hadrons produced in hard collisions and detected inclusively bear peculiar features: (i) they originate from jets whose initial virtuality and energy are of the same order; (ii) such jets are rare and have a very biased energy sharing among the particles, namely, the detected hadron carries the main fraction of the jet energy. The former feature leads to an extremely intensive gluon radiation and energy dissipation at the early stage of hadronization, either in vacuum or in a medium. As a result, a leading hadron must be produced on a short length scale. Evaluation within a model of perturbative fragmentation confirms the shortness of the production length. This result is at variance with the unjustified assumption of long production length, made within the popular energy loss scenario. Thus we conclude that the main reason of suppression of high-pT hadrons in heavy ion collisions is the controlled by color transparency attenuation of a high-pT dipole propagating through the hot medium. Adjusting a single parameter, the transport coefficient, we describe quite well the data from LHC and RHIC for the suppression factor RAA as function of pT , collision energy and centrality. We observe that the complementary effect of initial state interaction causes a flattening and even fall of RAA at large pT . The azimuthal anisotropy of hadron production, calculated with no further adjustment, also agrees well with data at different energies and centralities.

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“…Compared to the current modeling of parton energy loss [2][3][4][5][6][7], this will be seen to result in a characteristic softening of the ensuing hadronization. It may, thus, affect significantly the extraction of medium properties from the measured nuclear modification factor at the LHC [8][9][10].We start by considering an elementary building block of a parton shower, the q → q g parton splitting. For a small light-cone energy k + of the gluon compared to the parent parton, x ≡ k + /p + 1, and for transverse gluon momentum k with K 0 ≡ k/k 2 , the gluon spectrum reads, to leading order in α s ,…”

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confidence: 99%

Medium-induced color flow softens hadronization

2012

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Medium-induced parton energy loss, resulting from gluon exchanges between the QCD matter and partonic projectiles, is expected to underlie the strong suppression of jets and high-p T hadron spectra observed in ultrarelativistic heavy-ion collisions. Here, we present the first color-differential calculation of parton energy loss. We find that color exchange between medium and projectile decoheres the color of radiated gluons from that of the most energetic fragments and enhances parametrically the invariant mass of energetic color singlet clusters in the parton shower. These effects are seen in more than half of the medium-modified parton branchings. As shown for a cluster hadronization model and as argued for a Lund string fragmentation model, this leads to additional softening of hadronic spectra. Compared to standard parton energy loss calculations, a lower density of the QCD matter is then needed to account for the nuclear modification factor at the Large Hadron Collider. High-transverse-momentum partons (p T 10 GeV) produced in heavy-ion collisions interact with the QCD matter in the collision region while branching. This interaction is thought to cause the strong medium modification of hadronic spectra and jets measured in heavy-ion collisions at the Large Hadron Collider (LHC) and at the Relativistic Heavy Ion Collider. The modeling of this jet quenching phenomenon has focused so far on medium-induced parton energy loss prior to hadronization [1], assuming that, for sufficiently high p T , hadronization occurs time delayed and thus outside the medium. However, if the color flow of a parton shower is modified within the medium, then hadronization can be affected irrespective of when it occurs. Here, we analyze the medium-induced color flow in a standard parton-energy-loss calculation. Compared to the current modeling of parton energy loss [2][3][4][5][6][7], this will be seen to result in a characteristic softening of the ensuing hadronization. It may, thus, affect significantly the extraction of medium properties from the measured nuclear modification factor at the LHC [8][9][10].We start by considering an elementary building block of a parton shower, the q → q g parton splitting. For a small light-cone energy k + of the gluon compared to the parent parton, x ≡ k + /p + 1, and for transverse gluon momentum k with K 0 ≡ k/k 2 , the gluon spectrum reads, to leading order in α s ,In the presence of QCD matter, interactions between projectile parton and medium result in a modified spectrum dI rad ≡ dI vac + dI med that can be written as an expansion in powers of the ratio ζ ≡ L + /λ + el of the in-medium path length L + and an elastic mean free path λ + el (for details, see Ref.[1]). To first order in this opacity expansion, the medium-induced radiation spectrum readswhere · · · denotes averaging over the transverse-momentum transfer q of a single interaction andMedium-induced interference effects enter via the factorThus, the medium-modification dI med can occur only for quanta of sufficiently small formation...

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Nuclear modification factors from the CMS experiment

Cited by 23 publications

References 35 publications

Quarkonia measurements by the CMS experiment in PbPb collisions

Quarkonia measurements by the CMS experiment in PbPb collisions

Quenching of high-pThadrons: Energy loss versus color transparency

Medium-induced color flow softens hadronization

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